code: protected boolean isReserved( String name ) {
          if( functions.isFunctionName(name))
              return true;
  
          for (int i = 0; i < name.length(); i++) {
              if( !isLetter(name.charAt(i)) )
                  return true;
          }
          return false;
      }
docs: Returns true if the specified name is NOT allowed.  It isn't allowed if it matches a built in operator
  or if it contains a restricted character.