diff --git a/include/xo/expression/Apply.hpp b/include/xo/expression/Apply.hpp
index 161806fc..003b49fa 100644
--- a/include/xo/expression/Apply.hpp
+++ b/include/xo/expression/Apply.hpp
@@ -129,7 +129,7 @@ namespace xo {
                 return xform_fn(this);
             }
 
-            virtual void attach_envs(bp<Environment> p) override;
+            virtual void attach_envs(bp<SymbolTable> p) override;
 
             virtual void display(std::ostream & os) const override;
             virtual std::uint32_t pretty_print(const ppindentinfo & ppii) const override;
diff --git a/include/xo/expression/AssignExpr.hpp b/include/xo/expression/AssignExpr.hpp
index 0672e8c2..2fe947ba 100644
--- a/include/xo/expression/AssignExpr.hpp
+++ b/include/xo/expression/AssignExpr.hpp
@@ -37,7 +37,7 @@ namespace xo {
             virtual std::size_t visit_preorder(VisitFn visitor_fn) override;
             virtual std::size_t visit_layer(VisitFn visitor_fn) override;
             virtual rp<Expression> xform_layer(TransformFn xform_fn) override;
-            virtual void attach_envs(bp<Environment> p) override;
+            virtual void attach_envs(bp<SymbolTable> p) override;
 
             virtual void display(std::ostream & os) const override;
             virtual std::uint32_t pretty_print(const ppindentinfo & ppii) const override;
diff --git a/include/xo/expression/ConstantInterface.hpp b/include/xo/expression/ConstantInterface.hpp
index 474f8f3f..57db19b8 100644
--- a/include/xo/expression/ConstantInterface.hpp
+++ b/include/xo/expression/ConstantInterface.hpp
@@ -40,7 +40,7 @@ namespace xo {
                 return std::set<std::string>();
             }
 
-            virtual void attach_envs(bp<Environment> /*p*/) override {}
+            virtual void attach_envs(bp<SymbolTable> /*p*/) override {}
 
         }; /*ConstantInterface*/
 
diff --git a/include/xo/expression/ConvertExpr.hpp b/include/xo/expression/ConvertExpr.hpp
index 9b6808bf..26f5c337 100644
--- a/include/xo/expression/ConvertExpr.hpp
+++ b/include/xo/expression/ConvertExpr.hpp
@@ -61,7 +61,7 @@ namespace xo {
                 return xform_fn(this);
             }
 
-            virtual void attach_envs(bp<Environment> p) override {
+            virtual void attach_envs(bp<SymbolTable> p) override {
                 arg_->attach_envs(p);
             }
 
diff --git a/include/xo/expression/DefineExpr.hpp b/include/xo/expression/DefineExpr.hpp
index 5df7ea1a..085c18ce 100644
--- a/include/xo/expression/DefineExpr.hpp
+++ b/include/xo/expression/DefineExpr.hpp
@@ -75,7 +75,7 @@ namespace xo {
                 return xform_fn(this);
             }
 
-            virtual void attach_envs(bp<Environment> p) override {
+            virtual void attach_envs(bp<SymbolTable> p) override {
                 rhs_->attach_envs(p);
             }
 
diff --git a/include/xo/expression/Expression.hpp b/include/xo/expression/Expression.hpp
index 07ac6afe..15fad60c 100644
--- a/include/xo/expression/Expression.hpp
+++ b/include/xo/expression/Expression.hpp
@@ -13,7 +13,7 @@ namespace xo {
     namespace scm {
         class Variable; /* see Variable.hpp */
         class Lambda;   /* see Lamnbda.hpp */
-        class Environment; /* see Environment.hpp */
+        class SymbolTable; /* see SymbolTable.hpp */
 
         /** @class Expression
          *  @brief abstract syntax tree for an EGAD program
@@ -72,7 +72,7 @@ namespace xo {
              *    from @p X.argv
              *  - resolve free variables from @p parent
              **/
-            virtual void attach_envs(bp<Environment> parent) = 0;
+            virtual void attach_envs(bp<SymbolTable> parent) = 0;
 
             /** append to *p_set the set of free variables in this expression.
              *  returns the number of free variables introduced
diff --git a/include/xo/expression/GlobalEnv.hpp b/include/xo/expression/GlobalSymtab.hpp
similarity index 88%
rename from include/xo/expression/GlobalEnv.hpp
rename to include/xo/expression/GlobalSymtab.hpp
index 2670f929..6bdd88e0 100644
--- a/include/xo/expression/GlobalEnv.hpp
+++ b/include/xo/expression/GlobalSymtab.hpp
@@ -1,20 +1,20 @@
-/* file GlobalEnv.hpp
+/* file GlobalSymtab.hpp
  *
  * author: Roland Conybeare, Jun 2024
  */
 
 #pragma once
 
-#include "Environment.hpp"
+#include "SymbolTable.hpp"
 #include <map>
 #include <string>
 
 namespace xo {
     namespace scm {
-        class GlobalEnv : public Environment {
+        class GlobalSymtab : public SymbolTable {
         public:
             /** create instance.  Probably only need one of these **/
-            static rp<GlobalEnv> make_empty() { return new GlobalEnv(); }
+            static rp<GlobalSymtab> make_empty() { return new GlobalSymtab(); }
 
             bp<Expression> require_global(const std::string & vname,
                                           bp<Expression> expr);
@@ -51,7 +51,7 @@ namespace xo {
             virtual std::uint32_t pretty_print(const xo::print::ppindentinfo & ppii) const override;
 
         private:
-            GlobalEnv();
+            GlobalSymtab();
 
         private:
             /* for assignable globals,  need to allocate memory
@@ -63,4 +63,4 @@ namespace xo {
 } /*namespace xo*/
 
 
-/* end GlobalEnv.hpp */
+/* end GlobalSymtab.hpp */
diff --git a/include/xo/expression/IfExpr.hpp b/include/xo/expression/IfExpr.hpp
index b6dd0cc9..6ce220fc 100644
--- a/include/xo/expression/IfExpr.hpp
+++ b/include/xo/expression/IfExpr.hpp
@@ -87,7 +87,7 @@ namespace xo {
                 return xform_fn(this);
             }
 
-            virtual void attach_envs(bp<Environment> p) override {
+            virtual void attach_envs(bp<SymbolTable> p) override {
                 test_->attach_envs(p);
                 when_true_->attach_envs(p);
                 when_false_->attach_envs(p);
diff --git a/include/xo/expression/Lambda.hpp b/include/xo/expression/Lambda.hpp
index 0b480d8f..81a872b6 100644
--- a/include/xo/expression/Lambda.hpp
+++ b/include/xo/expression/Lambda.hpp
@@ -8,7 +8,7 @@
 #include "Expression.hpp"
 #include "FunctionInterface.hpp"
 #include "Variable.hpp"
-#include "LocalEnv.hpp"
+#include "LocalSymtab.hpp"
 #include <map>
 #include <vector>
 #include <string>
@@ -30,7 +30,7 @@ namespace xo {
              **/
             static rp<Lambda> make(const std::string & name,
                                    TypeDescr lambda_type,
-                                   const rp<LocalEnv> & local_env,
+                                   const rp<LocalSymtab> & local_env,
                                    const rp<Expression> & body);
 
             /**
@@ -42,7 +42,7 @@ namespace xo {
             static rp<Lambda> make(const std::string & name,
                                    const std::vector<rp<Variable>> & argv,
                                    const rp<Expression> & body,
-                                   const rp<Environment> & parent_env);
+                                   const rp<SymbolTable> & parent_env);
 
             /**
              *  @p name   Name for this lambda -- must be unique
@@ -50,7 +50,7 @@ namespace xo {
              *  @p body   Expression for body of function
              **/
             static rp<Lambda> make_from_env(const std::string & name,
-                                            const rp<LocalEnv> & env,
+                                            const rp<LocalSymtab> & env,
                                             TypeDescr explicit_return_td,
                                             const rp<Expression> & body);
 
@@ -122,7 +122,7 @@ namespace xo {
                 return this;
             }
 
-            virtual void attach_envs(bp<Environment> p) override;
+            virtual void attach_envs(bp<SymbolTable> p) override;
 
             virtual void display(std::ostream & os) const override;
             virtual std::uint32_t pretty_print(const ppindentinfo & ppii) const override;
@@ -138,7 +138,7 @@ namespace xo {
              **/
             Lambda(const std::string & name,
                    TypeDescr lambda_type,
-                   const rp<LocalEnv> & local_env,
+                   const rp<LocalSymtab> & local_env,
                    const rp<Expression> & body);
 
             /** compute free-variable set for this lambda **/
@@ -201,14 +201,14 @@ namespace xo {
              * when Lambda constructor runs,  so we need to assign @ref local_env_
              * later.
              **/
-            rp<LocalEnv> local_env_;
+            rp<LocalSymtab> local_env_;
         }; /*Lambda*/
 
         inline rp<Lambda>
         make_lambda(const std::string & name,
                     const std::vector<rp<Variable>> & argv,
                     const rp<Expression> & body,
-                    const rp<Environment> & parent_env)
+                    const rp<SymbolTable> & parent_env)
         {
             return Lambda::make(name, argv, body, parent_env);
         }
@@ -218,7 +218,7 @@ namespace xo {
             static rp<LambdaAccess> make(const std::string & name,
                                          const std::vector<rp<Variable>> & argv,
                                          const rp<Expression> & body,
-                                         const rp<Environment> & parent_env);
+                                         const rp<SymbolTable> & parent_env);
             static rp<LambdaAccess> make_empty();
 
             /** assign body + compute derived members
@@ -232,7 +232,7 @@ namespace xo {
              **/
             LambdaAccess(const std::string & name,
                          TypeDescr lambda_type,
-                         const rp<LocalEnv> & local_env,
+                         const rp<LocalSymtab> & local_env,
                          const rp<Expression> & body);
 
 
diff --git a/include/xo/expression/LocalEnv.hpp b/include/xo/expression/LocalSymtab.hpp
similarity index 76%
rename from include/xo/expression/LocalEnv.hpp
rename to include/xo/expression/LocalSymtab.hpp
index dc500f37..6fd4e395 100644
--- a/include/xo/expression/LocalEnv.hpp
+++ b/include/xo/expression/LocalSymtab.hpp
@@ -1,11 +1,11 @@
-/* file LocalEnv.hpp
+/* file LocalSymtab.hpp
  *
  * author: Roland Conybeare, Jun 2024
  */
 
 #pragma once
 
-#include "Environment.hpp"
+#include "SymbolTable.hpp"
 #include "Variable.hpp"
 #include "xo/reflect/TypeDescr.hpp"
 
@@ -20,20 +20,20 @@ namespace xo {
          *  parameters,  but also links to @ref Environment for
          *  innermost enclosing @ref Lambda.
          **/
-        class LocalEnv : public Environment {
+        class LocalSymtab : public SymbolTable {
         public:
             using TypeDescr = xo::reflect::TypeDescr;
 
         public:
-            static rp<LocalEnv> make_empty();
+            static rp<LocalSymtab> make_empty();
             /** named ctor idiom.  Create instance with local variables per @p argv **/
-            static rp<LocalEnv> make(const std::vector<rp<Variable>> & argv,
-                                     const rp<Environment> & parent_env);
+            static rp<LocalSymtab> make(const std::vector<rp<Variable>> & argv,
+                                        const rp<SymbolTable> & parent_env);
             /** Create instance with single local variable @ap argv1 **/
-            static rp<LocalEnv> make1(const rp<Variable> & arg1,
-                                      const rp<Environment> & parent_env);
+            static rp<LocalSymtab> make1(const rp<Variable> & arg1,
+                                         const rp<SymbolTable> & parent_env);
             /** runtime downcast. nullptr if @p x is not a LocalEnv instance **/
-            static bp<LocalEnv> from(const bp<Environment> & x) { return bp<LocalEnv>::from(x); }
+            static bp<LocalSymtab> from(const bp<SymbolTable> & x) { return bp<LocalSymtab>::from(x); }
 
             Lambda * origin() const { return origin_; }
             const std::vector<rp<Variable>> & argv() const { return argv_; }
@@ -53,7 +53,7 @@ namespace xo {
             }
 
             /** single-assign this environment's parent **/
-            void assign_parent(bp<Environment> p);
+            void assign_parent(bp<SymbolTable> p);
 
             // ----- Environment -----
 
@@ -91,7 +91,7 @@ namespace xo {
             virtual std::uint32_t pretty_print(const print::ppindentinfo & ppii) const override;
 
         private:
-            LocalEnv(const std::vector<rp<Variable>> & argv, const rp<Environment> & parent_env);
+            LocalSymtab(const std::vector<rp<Variable>> & argv, const rp<SymbolTable> & parent_env);
 
         private:
             /** Lambda for which this environment created.
@@ -103,17 +103,21 @@ namespace xo {
              **/
             Lambda * origin_ = nullptr;
 
-            /** formal argument names **/
+            /** formal argument names.
+             *  all variables in @ref argv_ have distinct names.
+             *  if @c .lookup_binding(vname) returns a binding path with @c .i_link=0 and @c .j_slot=j
+             *  then @c argv_[j]->name_ is @c vname.
+             **/
             std::vector<rp<Variable>> argv_;
 
             /** parent environment.  A free variable in this lambda's
              *  body will be resolved by referring them to @ref parent_env_.
              **/
-            rp<Environment> parent_env_;
+            rp<SymbolTable> parent_env_;
         };
 
     } /*namespace scm*/
 } /*namespace xo*/
 
 
-/* end LocalEnv.hpp */
+/* end LocalSymtab.hpp */
diff --git a/include/xo/expression/PrimitiveInterface.hpp b/include/xo/expression/PrimitiveInterface.hpp
index 2654a535..c9e5660e 100644
--- a/include/xo/expression/PrimitiveInterface.hpp
+++ b/include/xo/expression/PrimitiveInterface.hpp
@@ -66,7 +66,7 @@ namespace xo {
                 return xform_fn(this);
             }
 
-            virtual void attach_envs(bp<Environment> /*p*/) override {}
+            virtual void attach_envs(bp<SymbolTable> /*p*/) override {}
 
         private:
         }; /*PrimitiveInterface*/
diff --git a/include/xo/expression/Sequence.hpp b/include/xo/expression/Sequence.hpp
index 416c0c6c..c713eb3d 100644
--- a/include/xo/expression/Sequence.hpp
+++ b/include/xo/expression/Sequence.hpp
@@ -32,7 +32,7 @@ namespace xo {
             /** note: borken if .expr_v_ contains any def-exprs **/
             virtual std::size_t visit_layer(VisitFn visitor_fn) override;
             virtual rp<Expression> xform_layer(TransformFn visitor_fn) override;
-            virtual void attach_envs(bp<Environment> parent) override;
+            virtual void attach_envs(bp<SymbolTable> parent) override;
 
             // ----- from GeneralizedExpression ----
 
diff --git a/include/xo/expression/Environment.hpp b/include/xo/expression/SymbolTable.hpp
similarity index 93%
rename from include/xo/expression/Environment.hpp
rename to include/xo/expression/SymbolTable.hpp
index f3f482e4..710a3c0f 100644
--- a/include/xo/expression/Environment.hpp
+++ b/include/xo/expression/SymbolTable.hpp
@@ -1,4 +1,4 @@
-/* file Environment.hpp
+/* file SymbolTable.hpp
  *
  * author: Roland Conybeare, Jun 2024
  */
@@ -22,7 +22,7 @@ namespace xo {
          *  When generating code (see xo-jit): rhs can be any expression,
          *  for example a Lambda.
          **/
-        class Environment : public ref::Refcount {
+        class SymbolTable : public ref::Refcount {
         public:
             /** true if this is toplevel (global) environment.
              *  Toplevel environment doesn't have slot numbers.
@@ -57,7 +57,7 @@ namespace xo {
         };
 
         inline std::ostream &
-        operator<< (std::ostream & os, const Environment & x) {
+        operator<< (std::ostream & os, const SymbolTable & x) {
             x.print(os);
             return os;
         }
@@ -65,4 +65,4 @@ namespace xo {
 } /*namespace xo*/
 
 
-/* end Environment.hpp */
+/* end SymbolTable.hpp */
diff --git a/include/xo/expression/Variable.hpp b/include/xo/expression/Variable.hpp
index 846be5ab..f94452cd 100644
--- a/include/xo/expression/Variable.hpp
+++ b/include/xo/expression/Variable.hpp
@@ -64,7 +64,7 @@ namespace xo {
                 return xform_fn(this);
             }
 
-            virtual void attach_envs(bp<Environment> /*p*/) override;
+            virtual void attach_envs(bp<SymbolTable> /*p*/) override;
 
             virtual void display(std::ostream & os) const override;
             virtual std::uint32_t pretty_print(const ppindentinfo & ppii) const override;
diff --git a/include/xo/expression/pretty_localenv.hpp b/include/xo/expression/pretty_localenv.hpp
index 7a09b187..779ce96c 100644
--- a/include/xo/expression/pretty_localenv.hpp
+++ b/include/xo/expression/pretty_localenv.hpp
@@ -4,32 +4,32 @@
 
 #include "xo/indentlog/print/pretty.hpp"
 #include "xo/refcnt/pretty_refcnt.hpp"
-#include "LocalEnv.hpp"
+#include "LocalSymtab.hpp"
 
 namespace xo {
     namespace print {
         template <>
-        struct ppdetail<xo::scm::Environment> {
-            static bool print_pretty(const ppindentinfo & ppii, const xo::scm::Environment & x) {
+        struct ppdetail<xo::scm::SymbolTable> {
+            static bool print_pretty(const ppindentinfo & ppii, const xo::scm::SymbolTable & x) {
                 return x.pretty_print(ppii);
             }
         };
 
         template <>
-        struct ppdetail<xo::scm::LocalEnv> {
-            static bool print_pretty(const ppindentinfo & ppii, const xo::scm::LocalEnv & x) {
+        struct ppdetail<xo::scm::LocalSymtab> {
+            static bool print_pretty(const ppindentinfo & ppii, const xo::scm::LocalSymtab & x) {
                 return x.pretty_print(ppii);
             }
         };
 
         template <>
-        struct ppdetail<xo::scm::LocalEnv*> {
-            static bool print_pretty(const ppindentinfo & ppii, const xo::scm::LocalEnv* x) {
+        struct ppdetail<xo::scm::LocalSymtab*> {
+            static bool print_pretty(const ppindentinfo & ppii, const xo::scm::LocalSymtab* x) {
                 if (x) {
                     return x->pretty_print(ppii);
                 } else {
                     ppii.pps()->write("<nullptr ");
-                    ppii.pps()->write(reflect::type_name<xo::scm::LocalEnv>());
+                    ppii.pps()->write(reflect::type_name<xo::scm::LocalSymtab>());
                     ppii.pps()->write(">");
                     return ppii.pps()->has_margin();
                 }
diff --git a/src/expression/Apply.cpp b/src/expression/Apply.cpp
index 91172c63..1a205b86 100644
--- a/src/expression/Apply.cpp
+++ b/src/expression/Apply.cpp
@@ -149,7 +149,7 @@ namespace xo {
         }
 
         void
-        Apply::attach_envs(bp<Environment> p) {
+        Apply::attach_envs(bp<SymbolTable> p) {
             fn_->attach_envs(p);
 
             for (const auto & arg : argv_)
diff --git a/src/expression/AssignExpr.cpp b/src/expression/AssignExpr.cpp
index 26dc7bed..ce68014c 100644
--- a/src/expression/AssignExpr.cpp
+++ b/src/expression/AssignExpr.cpp
@@ -77,7 +77,7 @@ namespace xo {
         }
 
          void
-         AssignExpr::attach_envs(bp<Environment> p) {
+         AssignExpr::attach_envs(bp<SymbolTable> p) {
              lhs_->attach_envs(p);
              rhs_->attach_envs(p);
          }
diff --git a/src/expression/CMakeLists.txt b/src/expression/CMakeLists.txt
index 57ba0b03..d2a9a7e1 100644
--- a/src/expression/CMakeLists.txt
+++ b/src/expression/CMakeLists.txt
@@ -11,8 +11,8 @@ set(SELF_SRCS
     Variable.cpp
     IfExpr.cpp
     Sequence.cpp
-    GlobalEnv.cpp
-    LocalEnv.cpp
+    GlobalSymtab.cpp
+    LocalSymtab.cpp
     ConvertExpr.cpp
     Primitive.cpp
     typeinf/type_ref.cpp
diff --git a/src/expression/GlobalEnv.cpp b/src/expression/GlobalSymtab.cpp
similarity index 79%
rename from src/expression/GlobalEnv.cpp
rename to src/expression/GlobalSymtab.cpp
index 14e9a4e8..93a27624 100644
--- a/src/expression/GlobalEnv.cpp
+++ b/src/expression/GlobalSymtab.cpp
@@ -4,15 +4,15 @@
  */
 
 #include "xo/indentlog/print/ppdetail_atomic.hpp"
-#include "GlobalEnv.hpp"
+#include "GlobalSymtab.hpp"
 #include "Expression.hpp"
 
 namespace xo {
     namespace scm {
-        GlobalEnv::GlobalEnv() = default;
+        GlobalSymtab::GlobalSymtab() = default;
 
         bp<Expression>
-        GlobalEnv::require_global(const std::string & vname,
+        GlobalSymtab::require_global(const std::string & vname,
                                   bp<Expression> expr)
         {
             this->global_map_[vname] = expr.get();
@@ -21,21 +21,21 @@ namespace xo {
         } /*require_global*/
 
         void
-        GlobalEnv::upsert_local(bp<Variable> target) {
+        GlobalSymtab::upsert_local(bp<Variable> target) {
             // in practice: paraphrase of .require_global()
 
             this->global_map_[target->name()] = target.promote();
         }
 
         void
-        GlobalEnv::print(std::ostream & os) const {
+        GlobalSymtab::print(std::ostream & os) const {
             os << "<GlobalEnv"
                << xtag("size", global_map_.size())
                << ">";
         }
 
         std::uint32_t
-        GlobalEnv::pretty_print(const xo::print::ppindentinfo & ppii) const
+        GlobalSymtab::pretty_print(const xo::print::ppindentinfo & ppii) const
         {
             using xo::print::ppstate;
 
diff --git a/src/expression/Lambda.cpp b/src/expression/Lambda.cpp
index 3988d9c9..7a140f04 100644
--- a/src/expression/Lambda.cpp
+++ b/src/expression/Lambda.cpp
@@ -87,7 +87,7 @@ namespace xo {
         rp<Lambda>
         Lambda::make(const std::string & name,
                      TypeDescr lambda_td,
-                     const rp<LocalEnv> & env,
+                     const rp<LocalSymtab> & env,
                      const rp<Expression> & body)
         {
             return new Lambda(name, lambda_td, env, body);
@@ -95,7 +95,7 @@ namespace xo {
 
         rp<Lambda>
         Lambda::make_from_env(const std::string & name,
-                              const rp<LocalEnv> & env,
+                              const rp<LocalSymtab> & env,
                               TypeDescr explicit_return_td,
                               const rp<Expression> & body)
         {
@@ -117,9 +117,9 @@ namespace xo {
         Lambda::make(const std::string & name,
                      const std::vector<rp<Variable>> & argv,
                      const rp<Expression> & body,
-                     const rp<Environment> & parent_env)
+                     const rp<SymbolTable> & parent_env)
         {
-            rp<LocalEnv> env = LocalEnv::make(argv, parent_env);
+            rp<LocalSymtab> env = LocalSymtab::make(argv, parent_env);
 
             TypeDescr explicit_return_td = nullptr;
 
@@ -257,7 +257,7 @@ namespace xo {
 
         Lambda::Lambda(const std::string & name,
                        TypeDescr lambda_td,
-                       const rp<LocalEnv> & local_env,
+                       const rp<LocalSymtab> & local_env,
                        const rp<Expression> & body)
             : FunctionInterface(exprtype::lambda, lambda_td),
               name_{name},
@@ -334,7 +334,7 @@ namespace xo {
         } /*ctor*/
 
         void
-        Lambda::attach_envs(bp<Environment> p) {
+        Lambda::attach_envs(bp<SymbolTable> p) {
             local_env_->assign_parent(p);
 
             /** establish a binding path for each variable **/
@@ -364,11 +364,11 @@ namespace xo {
         LambdaAccess::make(const std::string & name,
                            const std::vector<rp<Variable>> & argv,
                            const rp<Expression> & body,
-                           const rp<Environment> & parent_env)
+                           const rp<SymbolTable> & parent_env)
         {
             TypeDescr explicit_return_td = nullptr;
             TypeDescr lambda_td = assemble_lambda_td(argv, explicit_return_td, body);
-            rp<LocalEnv> env = LocalEnv::make(argv, parent_env);
+            rp<LocalSymtab> env = LocalSymtab::make(argv, parent_env);
 
             rp<LambdaAccess> retval
                 = new LambdaAccess(name,
@@ -393,7 +393,7 @@ namespace xo {
 
         LambdaAccess::LambdaAccess(const std::string & name,
                                    TypeDescr lambda_td,
-                                   const rp<LocalEnv> & local_env,
+                                   const rp<LocalSymtab> & local_env,
                                    const rp<Expression> & body)
             : Lambda(name, lambda_td, local_env, body)
         {}
diff --git a/src/expression/LocalEnv.cpp b/src/expression/LocalSymtab.cpp
similarity index 67%
rename from src/expression/LocalEnv.cpp
rename to src/expression/LocalSymtab.cpp
index 278ea88c..db5f67b9 100644
--- a/src/expression/LocalEnv.cpp
+++ b/src/expression/LocalSymtab.cpp
@@ -1,9 +1,9 @@
-/* file LocalEnv.cpp
+/* file LocalSymtab.cpp
  *
  * author: Roland Conybeare
  */
 
-#include "LocalEnv.hpp"
+#include "LocalSymtab.hpp"
 #include "pretty_variable.hpp"
 #include "xo/indentlog/print/pretty_vector.hpp"
 #include "xo/indentlog/print/vector.hpp"
@@ -11,29 +11,29 @@
 
 namespace xo {
     namespace scm {
-        rp<LocalEnv>
-        LocalEnv::make_empty() {
-            return new LocalEnv(std::vector<rp<Variable>>(), nullptr);
+        rp<LocalSymtab>
+        LocalSymtab::make_empty() {
+            return new LocalSymtab(std::vector<rp<Variable>>(), nullptr);
         }
 
-        rp<LocalEnv>
-        LocalEnv::make(const std::vector<rp<Variable>> & argv,
-                       const rp<Environment> & parent_env)
+        rp<LocalSymtab>
+        LocalSymtab::make(const std::vector<rp<Variable>> & argv,
+                       const rp<SymbolTable> & parent_env)
         {
-            return new LocalEnv(argv, parent_env);
+            return new LocalSymtab(argv, parent_env);
         }
 
-        rp<LocalEnv>
-        LocalEnv::make1(const rp<Variable> & arg1,
-                        const rp<Environment> & parent_env)
+        rp<LocalSymtab>
+        LocalSymtab::make1(const rp<Variable> & arg1,
+                        const rp<SymbolTable> & parent_env)
         {
             std::vector<rp<Variable>> argv = { arg1 };
 
             return make(argv, parent_env);
         }
 
-        LocalEnv::LocalEnv(const std::vector<rp<Variable>> & argv,
-                           const rp<Environment> & parent_env)
+        LocalSymtab::LocalSymtab(const std::vector<rp<Variable>> & argv,
+                           const rp<SymbolTable> & parent_env)
             : origin_{nullptr},
               argv_(argv),
               parent_env_{parent_env}
@@ -43,7 +43,7 @@ namespace xo {
         }
 
         binding_path
-        LocalEnv::lookup_local_binding(const std::string & vname) const {
+        LocalSymtab::lookup_local_binding(const std::string & vname) const {
             int j_slot = 0;
             for (const auto & arg : argv_) {
                 if (arg->name() == vname)
@@ -55,7 +55,7 @@ namespace xo {
         } /*lookup_local_binding*/
 
         binding_path
-        LocalEnv::lookup_binding(const std::string & vname) const {
+        LocalSymtab::lookup_binding(const std::string & vname) const {
             {
                 auto local = this->lookup_local_binding(vname);
                 if (local.i_link_ == 0)
@@ -71,9 +71,9 @@ namespace xo {
         } /*lookup_binding*/
 
         void
-        LocalEnv::assign_parent(bp<Environment> p) {
+        LocalSymtab::assign_parent(bp<SymbolTable> p) {
             if ((parent_env_.get() != nullptr) && (parent_env_.get() != p.get())) {
-                throw std::runtime_error(tostr("LocalEnv::assign_parent(P2): already have established parent P1",
+                throw std::runtime_error(tostr("LocalSymtab::assign_parent(P2): already have established parent P1",
                                                xtag("P1", parent_env_),
                                                xtag("P2", p)));
 
@@ -84,7 +84,7 @@ namespace xo {
         }
 
         void
-        LocalEnv::upsert_local(bp<Variable> target) {
+        LocalSymtab::upsert_local(bp<Variable> target) {
             for (auto & var : this->argv_)  {
                 if (var->name() == target->name()) {
                     /* replace existing variable.  This may change its type */
@@ -99,20 +99,20 @@ namespace xo {
         }
 
         void
-        LocalEnv::print(std::ostream& os) const {
-            os << "<LocalEnv"
+        LocalSymtab::print(std::ostream& os) const {
+            os << "<LocalSymtab"
                << xtag("argv", argv_)
                << ">";
         }
 
         std::uint32_t
-        LocalEnv::pretty_print(const xo::print::ppindentinfo & ppii) const {
+        LocalSymtab::pretty_print(const xo::print::ppindentinfo & ppii) const {
             using xo::print::ppstate;
 
             ppstate * pps = ppii.pps();
 
             if (ppii.upto()) {
-                if (!pps->print_upto("<LocalEnv"))
+                if (!pps->print_upto("<LocalSymtab"))
                     return false;
                 if (!pps->print_upto_tag("argv", argv_))
                     return false;
@@ -120,7 +120,7 @@ namespace xo {
 
                 return true;
             } else {
-                pps->write("<LocalEnv");
+                pps->write("<LocalSymtab");
                 pps->newline_pretty_tag(ppii.ci1(), "this", (void*)this);
                 pps->newline_pretty_tag(ppii.ci1(), "argv", argv_);
                 pps->write(">");
@@ -132,5 +132,4 @@ namespace xo {
     } /*namespace scm*/
 } /*namespace xo*/
 
-
-/* end LocalEnv.cpp */
+/* end LocalSymtab.cpp */
diff --git a/src/expression/Sequence.cpp b/src/expression/Sequence.cpp
index cce57945..55a7d525 100644
--- a/src/expression/Sequence.cpp
+++ b/src/expression/Sequence.cpp
@@ -55,7 +55,7 @@ namespace xo {
         }
 
         void
-        Sequence::attach_envs(bp<Environment> p) {
+        Sequence::attach_envs(bp<SymbolTable> p) {
             for (const auto & x : expr_v_)
                 x->attach_envs(p);
         }
diff --git a/src/expression/Variable.cpp b/src/expression/Variable.cpp
index 903321d2..b44a9053 100644
--- a/src/expression/Variable.cpp
+++ b/src/expression/Variable.cpp
@@ -1,7 +1,7 @@
 /* @file Variable.cpp */
 
 #include "Variable.hpp"
-#include "Environment.hpp"
+#include "SymbolTable.hpp"
 #include "pretty_expression.hpp"
 
 namespace xo {
@@ -19,7 +19,7 @@ namespace xo {
         }
 
         void
-        Variable::attach_envs(bp<Environment> e) {
+        Variable::attach_envs(bp<SymbolTable> e) {
             /** e makes accessible all enclosing lexical scopes **/
             if (this->path_.i_link_ == -2 /*sentinel*/) {
                 this->path_ = e->lookup_binding(this->name_);