when (adv.)

Old English hwænne, hwenne, hwonne, from Proto-Germanic *hwan- (source also of Old Saxon hwan, Old Frisian hwenne, Middle Dutch wan, Old High German hwanne, German wann "when," wenn "if, whenever"), from pronominal stem *hwa-, from PIE root *kwo-, stem of relative and interrogative pronouns. Equivalent to Latin quom, cum. As a conjunction in late Old English. Say when "tell me when to stop pouring you this drink" is from 1889.