etymologeek.com dictionary
English word birthday comes from Old English ġebyrddæġ (also meaning "birth day"). The element ġebyrd (birth) may be related to the root "bear" while dæġ (day) derives from Proto-Germanic *dagaz, and Proto-Indo-European *dʰegʷʰ- ("to burn").

Birthday etymology history?

Birthday detailed word origin explanation

Dictionary entryLanguageDefinition
ġebyrd Old English (ang) birth
dæġ Old English (ang) day
ġebyrddæġ Old English (ang) birth day
birtheday Middle English (enm)
birthday English (eng) (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.

Words with the same origin as birthday

Descendants of ġebyrddæġ
birthday attack birthday cake birthday card birthday effect birthday girl birthday paradox birthday-suited half birthday happy birthday rebirthday unbirthday