chock [ME] A chock, as in ’chocks away!’, is a wedge or block placed against a wheel to prevent it from moving or to support it. It is probably from Middle French choque, meaning ‘block or log’. Chock-a-block [L18th], ‘crammed full’, was originally a nautical expression which referred to a pair of pulley blocks with ropes threaded between to form a hoist or tackle—when they have been pulled so close together that the two blocks touch, further lifting is impossible. The expression was probably influenced by chock-full [LME], a much older term meaning ‘filled to overflowing’. ‘Chock’ here is probably a form of choke (ME from Old English ceoce ‘jaw), from the idea of being so full that you are almost choking.