Why is “break a leg” a wish for good luck among theater folk? It comes from the German phrase hals-und beinbruch which means “neck and leg break” which means good luck.
That very well may have been a corruption of the Hebrew hatzlakha u-brakha meaning “success and blessing” which came to Germany via Yiddish. How did it end up in American entertainment? A lot of theater folk in early 20th century America were German-speaking immigrant Jews.