Green’s Dictionary of Slang

bunghole v.

1. to sodomize [bunghole n.1 (1)].

G. Legman Limericks 402: The height of my joys / Is bungholing boys.
[Scot]God Ship Venus in Bold (1979) 103: And every night by candlelight / They bung-holed one another!
[US]Guild Dict. Homosexual Terms 6: bunghole [...] (v.): To pedicate. The association with this meaning can be found in its original meaning, bung (ca. 1589): To close.
[US]C. Bukowski Erections, Ejaculations etc. 55: I want to bunghole you, you got those big cheeks.

2. (US drugs) to inject narcotics [Spears, Slang and Jargon of Drugs and Drink (1986), suggests ‘probably nonce’ but the term plays on the equation of narcotics and excrement, see shit n. (5)].

[US]J.E. Schmidt Narcotics Lingo and Lore.

3. (US) in fig. use of sense 1, to rob, to cheat, to exploit.

[US]L. Berney Whiplash River [ebook] ‘Mr. James robbed UNESCO blind. And every other NGO in Cambodia [...] He bung-holed them senseless’.

In derivatives

bungholer (n.)

(US) a sodomite, one who performs anal intercourse.

[US]G. Legman ‘Lang. Homosexuality’ in Henry Sex Variants II 1159: bungholer for pedicator.
[US]‘A. Edwardes’ Rape of India 53: [T]he Dorbach and Sepoy officer (whom Hámid describes as mutual ustání or bungholers) were hanged [Simes:DLSS].