The Sweeney is British slang for the Flying Squad, a special unit of the London police that deals with armed robbery and other serious crime — the officers who arrive fast, in cars, to catch criminals in the act. The name comes from Cockney rhyming slang: 'Sweeney Todd' rhymes with 'Flying Squad', and as rhyming slang usually does, it dropped the rhyming half and kept only the first word, leaving 'the Sweeney'. Sweeney Todd himself is a made-up character from old London stories, a barber who murdered his customers. The slang became widely known because of a rough, popular television drama called The Sweeney in the 1970s, full of car chases, shouting, and fights. Because of that show, people now use the name for a whole mood as well as for the police unit: if a street argument turns wild, someone might say 'it was like something out of The Sweeney'. It always takes 'the', it is informal, and it is a British word — Americans will not know it. Sweeney is also a common Irish family name, from Ó Suibhne, and that is where the character's name came from in the first place.