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Old English wanian "make or become smaller gradually," from Proto-Germanic *wanojanan (cf. Old Saxon wanon, Old Norse vana, Old Frisian wania, Middle Dutch waenen, Old High German wanon "to wane, to grow less"), from *wano- "lacking," from PIE *we-no-, from root *eue- "to leave, abandon, give out" (see vain). Related: Waned; waning; wanes.