What is the X in X-mas?
"medieval stone-throwing engine of war," c.1300 (in Anglo-Latin from early 13c.), from Old French trebuchet (12c.) "siege engine," from trabucher "to overturn, overthrow" (11c.), from tra- (from Latin trans-, here expressing "displacement") + Old French buc "trunk, bulk," from West Germanic *buh- (cf. German bauch "belly").