“Nalgas” is, at least in Mexico, slang for, er, the sittting-down parts. So “nalgadas” corresponds to “patadas” which means kicks, from “patas” which usually means paws or hooves but is slang for feet, or “punadas” (which should have a tilda squiggle over the n but my ipod doesn’t have tildas) "punch"from puno (also lacking a squiggle) which means fist.