THE OED appropriates Samuel Johnson’s definition (“The buttocks, the part on which we sit”), notes that it is “Not in polite use,” and offers a first citation from 1387.
The Google Ngram below shows the relative use of his bum (blue), her bum (red) and my bum (green) in American English books published from 1800-2008.
The chart is interesting to me for two reasons. First, it shows a fairly common pattern of frequent use of a British expression (or spelling) around 1800, declining for a hundred years (give or take), then increasing, slowly at first, then more rapidly in the last twenty or thirty years, the age of NOOBs. More subtle and surprising, to me, is the relative frequency of the three expressions. At first her is the most common by far and my is barely (no pun intended) used. But now the three forms are all about equal. Surely someone can make of this a monograph on sexuality and identity!
Runway falls don’t get any more straightforward than this: blame the shoes — again. The beauty of this clip, however, is the drunken-looking wobbly-ness of her recovery. The model in question falls on her bum, but looks like she might have bumped her head and seen some little birdies. (Time.com, February 13, 2009)/Up first was Rob Kardashian with a jazz-influenced cha-cha to “Walk Like A Man” from “Jersey Boys.” In practice, he asks partner Cheryl Burke to teach him to shake his bum like pro Maksim Chmerkovskiy. (Baltimore Sun, “Dancing with the Stars” blog, October 24, 2011)
Bum is definitely a Britishism, but is bottom (a word with which, surprisingly, it has nothing in common etymologically)? The OED dates it to about 1800 and cites all British sources, including this from Carlyle’s 1837 The French Revolution: “Patriot women take their hazel wands, and fustigate … broad bottoms of priests.”
Bottom is certainly commonly used in the U.S. now, often (oddly) either fully or semi-lasciviously or in addressing children, but also more straightforwardly, as in this 2003 New Yorker review of a Martha Graham dance performance: “I saw that Gary Galbraith, when he played the Minotaur, was provided with a pair of shorts that covered his bottom.“
I would appreciate your thoughts on whether bottom is a Britishism, as well as a vote in the poll below.