An Etymological Dictionary of the German Language/Annotated/wach
wach, adjective, ‘awake, on the alert,’ a remarkably late word (of the last century), which is entirely wanting in the earlier periods and dialects (in Middle High German wacker, see wacker); a recent derivative of wecken and wachen. The latter is an old form; compare Middle High German wachen, Old High German wahhên, ‘to wake, be awake,’ Old Saxon wakôn, Dutch waken, Anglo-Saxon wacian, wœččan, English to wake, watch; also in Gothic waken, strong verb, ‘to be awake, watch.’ For the early history of the cognates see the causative wecken. The abstract form Wache, feminine, ‘guard, watch,’ is from Middle High German (very rare) wache, for which wahte, feminine (Modern High German Wacht), is the usual term; to this Modern High German Wächter, masculine, ‘watch, guardian,’ from Middle High German wahtœ̂re is allied.