Here is a message I received from BranShea:
You are no pedant in this anniversary matter but simply right: We all have only one birthday i.e. the day we were born.
Only the English and the German language give: Birthday and Geburtstag (mentioning birth).
Dutch-verjaardag
French-anniversaire
Spanish-Cumpleaņos
Italian-anniversario
These four languages at least just give : the adding or passing of another year. Like what anniversary means.
So it is more correct to use anniversary than birthday.
Listen, you Bohemian Cur; listen and think: BranShea is excetionally bright and exceptionally kind (did you remember to thank her for her permission to post her personal message to you on this open board?) but she is not fully culturated in Americanisms.
The current term "birthday" was coined by two ladies who composed a song called "Happy Anniversary of your Birthday to You" but the song didn't sale so they changed the lyrics to "Happy Birthday to you" and the rest is history.
I accept your thanks for this information in advance as I do not wish you to grow up to be like Faldage who was 50 years old at the time of his birth.
