Schwantz Licker is an ancient term used for anyone who is a douchebag, ass hole, jerk off, etc. Schwantz meaning dick or penis so it's the equivalent to calling someone a dick licker.
Kevin: Hey Chuck why are you a schwantz licker?
Chuck: I don't know why?
Kevin: Cause schwantz is a cock and you love licking cock.
Chuck: I don't know why?
Kevin: Cause schwantz is a cock and you love licking cock.
by Kevin The Body December 2, 2008