Middle English word eo comes from Old English ēalā, Proto-Indo-European *h₁egʷʰ-, Proto-Indo-European *h₂ekʷeh₂, and later Proto-Indo-European *h₂ékʷeh₂ (Water.)
| Dictionary entry | Language | Definition |
|---|---|---|
| ēalā | Old English (ang) | |
| *h₁egʷʰ- | Proto-Indo-European (ine-pro) | |
| *h₂ekʷeh₂ | Proto-Indo-European (ine-pro) | |
| *h₂ékʷeh₂ | Proto-Indo-European (ine-pro) | Water. |
| *ahwō | Proto-Germanic (gem-pro) | Stream, river. Water. |
| *hē | Old English (ang) | |
| ea | Middle English (enm) |