Origin of the idiom keep at bay?

Answer 1

This is not really an idiom. Baying is a continuous barking by hounds. To keep something at bay means to prevent its escape by surrounding it with barking dogs, or by extension, to prevent a problem from getting out of control by maintaining constant vigilance.

Answer 2

To Stop or to wait!

Answer 3

It's not an idiom. "At bay" means helpless, in a corner where you can't get out. To hold at bay just means to corner or trap someone or something and keep it from moving or acting.