Barking Mad

A frequently repeated story claims this phrase comes from Barking, a town in Essex now part of East London, home to a medieval asylum attached to Barking Abbey where the mentally ill were supposedly sent, so someone acting strangely was said to be fit for "Barking." It's a tidy, place-name-based explanation. It's also almost certainly untrue: the phrase simply isn't recorded anywhere near the medieval period. The Oxford English Dictionary's earliest citation is from 1933, in a novel by Christine Pakenham, Countess of Longford, a full six hundred years after the supposed asylum connection would have taken hold. The much more mundane and much better supported explanation is that "barking" simply describes a person acting deranged enough to bark like a mad dog, in the same family as the older, well-established phrase "mad as a March hare."