‘Biter’ is a slang word for a cheat or swindler, e.g. a card-shaper. When he himself is cheated by his prospective victim, ‘the biter is bit’. In a general way, this refers to any form of retribution. As Laertes says in Shakespeare’s Hamlet after being wounded by the rapier that he himself has poisoned, ‘I am justly kill’d with my own treachery.’
