The floorboards are weakest where they 'butt' (against each other). [=where they meet, where the ends of the boards touch each other]
As a child, she was a clumsy girl who was the 'butt of' everyone's jokes. [=people made jokes about her because she was clumsy]
Why don't you 'get off your butt' and do something? [=why don't you stop being so lazy and do something?]
(..) - What makes you think she'll be there? - I read it in a book once. Cool. You handle the dragon. I'll handle the stairs. I'll fiind those stairs. I'll whip their butt too. Those stairs won't know which way they're goin'. I'm gonna take drastic steps. Kick it to the kerb. Don't mess (..)2001 Shrek
(..) need some Tic Tacs or something, 'cause your breath stinks! just like the time-- Then I ate some rotten berries. I had strong gases eking out of my butt that day. Why are you following me? I'll tell you why. 'Cause I'm all alone There's no one here beside me (..)2001 Shrek