Beat someone to the punch, come out swinging, come out fighting, down and out, down for the count, glass jaw, the gloves are off, go the distace, have someone in your corner, heavyweight / lightweight, heavy hitter, hit below the belt, in-fighting, kisser, knock-out (noun), K.O., low blow, on the ropes, one-two punch, the old one-two, pull one's punches, punch-drunk, punchy, ringside (judge/seat/table), roll with the punches, round, go a few rounds, saved by the bell, slap-happy, sparring partner, square off, sucker punch, knocking him into next Sunday, take a dive, take it on the chin, take off the gloves, take the count, throw in the towel, throw one's hat in the ring, work out.
I guess people just really liked boxing?