Middle English word oon comes from Proto-Indo-European *yo-, Proto-Indo-European - -nós, and later Proto-Indo-European *óynos (One. Single.)
| Dictionary entry | Language | Definition |
|---|---|---|
| *yo- | Proto-Indo-European (ine-pro) | |
| - -nós | Proto-Indo-European (ine-pro) | |
| *óynos | Proto-Indo-European (ine-pro) | One. Single. |
| *ainaz | Proto-Germanic (gem-pro) | (in the plural) some. (in the singular) one. |
| ānes | Old English (ang) | |
| oon | Middle English (enm) | One. |