diff --git a/doc/lispref/functions.texi b/doc/lispref/functions.texi
index c64ec3ea715..5444cea7fa9 100644
--- a/doc/lispref/functions.texi
+++ b/doc/lispref/functions.texi
@@ -674,6 +674,7 @@ variable; these two uses of a symbol are independent and do not
 conflict.  (This is not the case in some dialects of Lisp, like
 Scheme.)
 
+@cindex internal functions, naming conventions
   By convention, if a function's symbol consists of two names
 separated by @samp{--}, the function is intended for internal use and
 the first part names the file defining the function.  For example, a
diff --git a/doc/lispref/variables.texi b/doc/lispref/variables.texi
index 2f5ee037f3e..e89b28eb0c0 100644
--- a/doc/lispref/variables.texi
+++ b/doc/lispref/variables.texi
@@ -617,6 +617,8 @@ float-pi
 
 @node Tips for Defining
 @section Tips for Defining Variables Robustly
+@cindex variables, naming conventions
+@cindex naming conventions, variables
 
   When you define a variable whose value is a function, or a list of
 functions, use a name that ends in @samp{-function} or
@@ -659,6 +661,7 @@ The value is a whole shell command.
 @item @dots{}-switches
 The value specifies options for a command.
 
+@cindex internal variables, naming conventions
 @item @var{prefix}--@dots{}
 The variable is intended for internal use and is defined in the file
 @file{@var{prefix}.el}.  (Emacs code contributed before 2018 may