"to become awake," Old English wacan "to become awake," also from wacian "to be or remain awake," both from Proto-Germanic *waken (cf. Old Saxon wakon, Old Norse vaka, Danish vaage, Old Frisian waka, Dutch waken, Old High German wahhen, German wachen "to be awake," Gothic wakan "to watch"), from PIE root *weg- "to be strong, be lively" (cf. Sanskrit vajah "force, swiftness, race, prize," vajayati "drives on;" Latin vegere, vigere "to be live, be active, quicken," vigil "awake, wakeful," vigor "liveliness, activity"). Causative sense "to rouse from sleep" is attested from c.1300. Related: Waked; waking. Phrase wake-up call is attested from 1976, originally a call one received from the hotel desk in the morning.