bum

From Middle English bum (“buttocks, bottom”), a syncopated form of Middle English botym (“bottom”). Compare also Old Irish, Scottish Gaelic bun (“base, bottom”)

來自中世紀英文，英國稱為屁股，臀部。想像坐下來 (sit on your bum) ，乞丐都是坐下來乞討，引用變成乞丐，流浪漢，遊手好閒的人。