"to hear one who does not wish to be heard or what one is not meant to hear," 1540s, from over- + hear. The notion is perhaps "to hear beyond the intended range of the voice." Old English oferhieran (West Saxon), oferhēran (Anglian) also meant "to not listen, to disregard, disobey." Compare overlook (v.) for negative force of over; also Middle High German überhaeren, Middle Dutch overhoren in same sense. And Middle English had overheren "to hear fully or plainly" (c. 1300). The various senses reflect the wide range of over-. Related: Overheard; overhearing.