With all due respect, Cur, this is not pedantic, it's pathetic.

In the dictionary, if you look up the word (and I suggest you do) you will read: "the annual anniversary of the day on which a person was born, typically treated as an occasion for celebration and present-giving."

Birthday means precisely what you reject it for failing to accurately confer. All you are doing is insisting on a literal-minded interpretation of orthographical cognates over the accepted meaning of words—a prodigiously silly practice which runs into a wall whatever way you turn. Consider, for example, that consider means to examine stars.

You are adolescent all right. All too adolescent.