trebuchet (n.)

"medieval stone-throwing engine of war," c. 1300 (in Anglo-Latin from early 13c.), from Old French trebuchet (12c.) "stone-throwing siege engine," from trabuchier "to overturn, fall to the ground, overthrow" (11c.), from tra- (from Latin trans-, here expressing "displacement") + Old French buc "trunk, bulk," from Frankish *buk- "trunk of the body," from Proto-Germanic *bheu-, variant of *beu-, used in forming words loosely associated with swelling (such as German bauch "belly;" see bull (n.2)).