interjection, imitative of the sound of a hard hit, first recorded 1922 (from 1917 as the sound of an artillery shell bursting). Middle English had a verb bammen "to hit or strike" (late 14c.). A literary work from c.1450 represents the sound of repeated impact by Lus, bus! las, das!, and Middle English had lushe "a stroke, blow" (c.1400); lushen "to strike, knock, beat" (c.1300).