It does, but in US English it's used as a pejorative for someone who is lazy, unsuccessful, undesirable, etc. Historically it was used to refer to vagrants, drunks, and so on. 80-90 years ago the Brooklyn Dodgers became lovingly referred to as "Dem Bums," which just reflected the fact that they sucked. Nothing ass-related. On this side of the pond we don't often use it to mean butt, unless we're making fun of the Brits or something. Anyway, moving on.Well, "bum" already means "butt"