я правильно понимаю, что исторически все они [hw] и были?
Ну а откуда бы еще там эйч взялось?when
Old English hwænne, hwenne, hwonne, from Proto-Germanic *hwan- (cognates: 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 interrogative base *kwo- (see who). 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.who
Old English hwa "who," sometimes "what; anyone, someone; each; whosoever," from Proto-Germanic *hwas (cognates: Old Saxon hwe, Danish hvo, Swedish vem, Old Frisian hwa, Dutch wie, Old High German hwer, German wer, Gothic hvo (fem.) "who"), from PIE *kwo-, stem of relative and interrogative pronouns (cognates: Sanskrit kah "who, which;" Avestan ko, Hittite kuish "who;" Latin quis/quid "in what respect, to what extent; how, why," qua "where, which way," qui/quae/quod "who, which;" Lithuanian kas "who;" Old Church Slavonic kuto, Russian kto "who;" Old Irish ce, Welsh pwy "who"). what
Old English hwæt, referring to things in abstraction; also "why, wherefore; indeed, surely, truly," from Proto-Germanic pronoun *hwat (cognates: Old Saxon hwat, Old Norse hvat, Danish hvad, Old Frisian hwet, Dutch wat, Old High German hwaz, German was, Gothic hva "what"), from PIE *kwod, neuter singular of *kwos "who" (see who). Corresponding to Latin quid. where
Old English hwær, hwar "at what place," from Proto-Germanic adverb *hwar (cognates: Old Saxon hwar, Old Norse hvar, Old Frisian hwer, Middle Dutch waer, Old High German hwar, German wo, Gothic hvar "where"), equivalent to Latin cur, from PIE interrogative base *kwo- (see who).why
Old English hwi, instrumental case (indicating for what purpose or by what means) of hwæt (see what), from Proto-Germanic adverb *hwi (cognates: Old Saxon hwi, Old Norse hvi), from PIE *kwi- (source of Greek pei "where"), locative of *kwo- "who" (see who).