Green’s Dictionary of Slang

dork v.

[dork n. (1)]

(orig. US) of a man, to have sexual intercourse; thus n. dorker, one who has intercourse, a ‘fucker’.

[US]B. Rodgers Queens’ Vernacular.
[US] P. Munro Sl. U.
B. Moore Lex. Cadet Lang. 120/2: usage ‘Guess who’s the dorker of darkies?’ [ibid.] 121/1: usage ‘She really gets a kick out of it when I dork her up the arse’.

In phrases

ass-dork (v.)

(US) to sodomise, to have homosexual anal intercourse.

(con. 1988) A. Swofford Jarhead 44: If you’re a puffer, we’ll catch you ass-dorking in the shower or we’ll find the cock magazine under your rack.