Okay, I'm dumb. Whatever could they have possibly meant to say instead of "anus pounder"? (however intriguing that sounds!) "Angus" (which would involve bestiality), "bonus"...?

Anything with "pounder" in it sounds sexual to me. "Quarter pounder" always sounded like a very unsatisfactory night - coitus interruptus in technical terms. Either that, or a very small "instrument".