Middle English word bul comes from Proto-Indo-European *bʰōw-, Proto-Indo-European *bʰew-, Proto-Indo-European *bʰl̥no-, and later Proto-Germanic *būlō (Boil; sore.)
| Dictionary entry | Language | Definition |
|---|---|---|
| *bʰōw- | Proto-Indo-European (ine-pro) | |
| *bʰew- | Proto-Indo-European (ine-pro) | |
| *bʰl̥no- | Proto-Indo-European (ine-pro) | |
| *būlō | Proto-Germanic (gem-pro) | Boil; sore. |
| *būlǭ | Proto-Germanic (gem-pro) | Swelling; bump; boil. |
| *bulô | Proto-Germanic (gem-pro) | Bull. |
| bula | Old English (ang) | |
| *būlijǭ | Proto-Germanic (gem-pro) | |
| bȳl | Old English (ang) | |
| bile | Middle English (enm) |