Sucking the monkey

bung-hole

also bunghole, "hole in a cask through which is it filled, closed by a stopper," 1570s, from bung (n.) + hole (n.). Sense extended to "anus" by c. 1600.

"by c. 1600" means the first known written use was in ~1600. I wonder how fast the spoken use took. Months? It would have been the hot meme of the 1570s. I can imagine this convo in a pub.

"Guys, guys, guys. I was talking to the publican and I learned a new word. Bung means stopper, right? And hole - you know that one. What do you think bunghole means?"

2nd guy: "Dunno."

3rd guy: "Already know that. The stopper for a barrel. So?"

"How 'bout your anus?"

sucking the monkey from the bung hole