A slur towards/against Canadians, which only they can use. Call a Canadian this without being Canadian yourself and you'll find out just how quickly that politeness can die off.
American: Oh, yo, this is my Canadian friend, her name is Mae.
Mae: Haha, yeah, eh?
American 2: eeewww grooosss you brought a Maple Chugger in here??? Euuuughghghghghgh...
Mae: Now listen'ere bud, yer' makin' me a bit mad'ere, eh? How's aboot we take this to the rink, eh? I'll prove just how much of a hoser ye' are behind that hamburger-fucking face, bud.
American 2: She's a keeper.