Birch rod and Rod

Birch rod noun - A switch consisting of a twig or a bundle of twigs from a birch tree; used to hit people as punishment.

Rod and birch rod are semantically related. In some cases you can use "Rod" instead a noun phrase "Birch rod".

Rod noun - A heavy rigid stick used as a weapon or for punishment.

Birch rod and rod are semantically related. Sometimes you can replace phrase "Birch rod" with "Rod", this terms are similar.