I think it might be a reference to sodomy. As in you hit or "nock" the fart in the other persons anus with your penis.
Jimmy was such a phartnocker. On one occasion he nocked a fart so hard in Suzys anus that it backfired on his shaft.
by danny March 20, 2005
a really cool guy.
Man, Chris ain't no fartnocker. Chris is a phartnocker.
by Iroically, it's Chris. August 07, 2003