rename vars and add comment for clarity

Author: Nico Cernek

pandas/core/reshape/merge.py

@@ -1292,17 +1292,19 @@ def _get_join_indexers(left_keys, right_keys, sort=False, how="inner", **kwargs)
     # `count` is the num. of unique keys
     # set(lkey) | set(rkey) == range(count)
 
+    # flip left and right keys if performing a right merge
+    # to preserve right merge row order (GH 27453)
     if how == "right":
-        rkey, lkey, count = fkeys(rkey, lkey)
+        factorized_rkey, factorized_lkey, count = fkeys(rkey, lkey)
     else:
-        lkey, rkey, count = fkeys(lkey, rkey)
+        factorized_lkey, factorized_rkey, count = fkeys(lkey, rkey)
     # preserve left frame order if how == 'left' and sort == False
     kwargs = copy.copy(kwargs)
     if how == "left":
         kwargs["sort"] = sort
     join_func = _join_functions[how]
 
-    return join_func(lkey, rkey, count, **kwargs)
+    return join_func(factorized_lkey, factorized_rkey, count, **kwargs)
 
 
 def _restore_dropped_levels_multijoin(