Howdyphillip

Evidently, in the days of early vaudeville, the producers would book more performers than could possibly perform in the given time of the show - since "bad" acts could be pulled before their completion... so, in order to insure that the show didn't start paying people who don't actually perform, there was a general policy that a performer did NOT get paid unless they actually performed on-stage. So the phrase "break a leg" referred to breaking the visual plane of the legs that lined the side...