Middle English word why comes from Proto-Indo-European *kʷ-, Proto-Indo-European *kʷe-, Proto-Indo-European *kʷo-, and later Proto-Germanic *hwī (How, with what, by what means;.)
| Dictionary entry | Language | Definition |
|---|---|---|
| *kʷ- | Proto-Indo-European (ine-pro) | |
| *kʷe- | Proto-Indo-European (ine-pro) | |
| *kʷo- | Proto-Indo-European (ine-pro) | |
| *kʷód, kʷod | Proto-Indo-European (ine-pro) | |
| *hwī | Proto-Germanic (gem-pro) | How, with what, by what means;. |
| *kʷís | Proto-Indo-European (ine-pro) | Who, what (interrogative). Who, which, that (relative) Which, what. |
| *hwaz | Proto-Germanic (gem-pro) | (interrogative) who, what. (interrogative, in dative) whom. (interrogative, in genitive) whose. (interrogative, in instrumental) with whom, with what, how, in what way. |
| hwā | Old English (ang) | |
| hwī | Old English (ang) | |
| why | Middle English (enm) |