Bum

Chamber's Twientieth Century Dictionary · 1908 · p. 16

bum, n. ( Shak. ) the buttocks.— ns. Bum′-bail′iff , an under-bailiff; Bum′-boat , boat for carrying provisions to a ship, originally a Thames scavenger's boat. [Ety. dub., prob. from bump , from sense of 'swelling.']