English word birthday comes from Old English ġebyrddæġ (also meaning "birth day"). The element ġebyrd (birth) may be related to the root "to bear" while dæġ (day) ultimately derives from Proto-Germanic *dagaz, and Proto-Indo-European *dʰegʷʰ- ("to burn") with the idea that days are there when the sun is burning
| Dictionary entry | Language | Definition |
|---|---|---|
| ġebyrd | Old English (ang) | birth |
| dæġ | Old English (ang) | day |
| ġebyrddæġ | Old English (ang) | birth day |
| birtheday | Middle English (enm) | |
| birthday | English (en) | (intransitive, informal) To celebrate one's birthday. The anniversary of the day on which someone is born. [From 1570s]. The anniversary of the day on which something is created.. The date on which someone is born or something is created, more commonly called birthdate or date of birth. |