what

The story

1. Proto-Indo-European*kʷ-
2. Proto-Indo-European*kʷís
3. Proto-Germanic*hwat
4. Proto-West Germanic*hwat
5. Old Englishhwæt
6. Middle Englishwhat
7. English todaywhat

From Middle English what, from Old English hwæt (“what”), from Proto-West Germanic *hwat, from Proto-Germanic *hwat (“what”), from Proto-Indo-European *kʷód (“what”), neuter form of *kʷós (“who”). Cognate with Scots what, whit (“what”), North Frisian wat (“what”), Saterland Frisian wat (“what”), West Frisian wat (“what”), Dutch wat (“what”), Low German wat (“what”), German was (“what”), Danish hvad (“what”), Norwegian Bokmål hva (“what”), Swedish vad (“what”), Norwegian Nynorsk kva (“what”), Icelandic hvað (“what”), Latin quod (“what, which”). Its use as a particle of contradiction or objection in colloquial Malaysian and Singaporean Englishes is analogous to Malay apa and Cantonese 喎 /㖞 (wo³, etymology 2, sense 3). It is possible that this was historically reinforced by the dated use of what as a sentence-final question tag in British English.