noun
birch rod; switch
A bundle of twigs or a single branch used for corporal punishment, historically associated with discipline in schools or households.
昔の学校では、悪いことをすると枝鞭で叩かれることがあった。
In old schools, you could be hit with a birch rod if you did something bad.
鞭 is a general whip, while 枝鞭 specifically refers to a whip made from a tree branch or twigs.
Compound of 枝 (eda, 'branch') and 鞭 (muchi, 'whip'). The exact historical derivation is uncertain, but the word transparently describes a whip made from a branch.