who: [OE] Who goes right back to Indo-European *qwos, *qwes (source also of Russian kto ‘who’), whose neuter form *qwod gave English what. Its prehistoric Germanic descendant was *khwaz, *khwez, which has evolved into German wer, Dutch wie, Danish hvo, and English who. Whom comes from the Old English dative form hwǣm. [who etymology, who origin, 英语词源]