Bum/bummer

Bum is an old English word for posterior or buttocks and dates back to the 14th century. On the American side of the Atlantic, however, bum or bummer has meant a tramp or vagrant since the mid-19th century and when used as a verb, it means to laze around or sponge, as tramps do, as in ‘to bum a cigarette’. From the late 19th/early 20th century, bum also began to be used as an adjective meaning something poor, faulty or worthless as in ‘bum advice’. All these American usages have now spread to most English-speaking regions but have nothing whatsoever to do with the British usage meaning buttocks. The original American usages derive from the German bummler meaning a loafer or layabout. A more modern, slang usage of bummer means an unpleasant experience and sometimes an exclamation to this effect. Bummer in this sense dates from the 1960s and is still very much in vogue. See also Bum’s rush and Bum steer.