break a leg

The story

1. Hebrew · derived fromהַצְלָחָה וּבְרָכָה“success and blessing”
2. Yiddish · derived fromהצלחה און ברכה“success and blessing”
3. English todaybreak a leg

Unknown; many unproven and widely debated theories exist. One of the most plausible is that it comes from Yiddish הצלחה און ברכה (hatslokhe un brokhe, “success and blessing”) through the heavy Ashkenazi Jewish influence in the American theater, via the misinterpretation in German as Hals- und Beinbruch (“neck and leg fracture”). The Yiddish phrase itself comes from Hebrew הַצְלָחָה וּבְרָכָה (hatzlakhá u-v'rakhá, “success and blessing”). Another possible origin was to wish opposite luck on the performer so as not to jinx the statement.