nip these thoughts in the bud.
I definitely did not know this: Unless you're a guard dog, don't nip anyone in the butt! Nip it in the butt is just a mishearing of nip it in the bud — but this flowery phrase has nothing to do with rear ends or small, unused parts of something (two common meanings of butt). Even big publications get it wrong sometimes, as in this example:
In view of European history, the reverse would be the start of a very bitter road down a slippery slope and we have to nip this in the butt. (Time)
Ouch! To remember the correct expression, think of an unwanted weed or plant in the garden that you should nip in the bud before it grows out of control.
