Green’s Dictionary of Slang

(US) the buttocks, thus fig. oneself, e.g. in phr. get your bohunkus out of here!

1925		G.H. Mullin Adventures of a Scholar Tramp 82: His real name appeared to be Claphorne, ‘Cap’n Bohunkus’ being merely a jocular stroke of Frisco’s, which the old man accepted without a mite of resentment.
1956		L. Hughes Simply Heavenly I iv: I was the only one that got throwed out, and on my – bohunkus.
1960		Wodehouse Jeeves in the Offing 43: A guffin, which, I thought, having had time to ponder over it, would be something in the nature of a bohunkus or a hammerhead.
2000		C. Cook Robbers (2001) 335: Way he held her, way his bohunkus rolled around.