Input Junkie

I have always supposed that the Wizarding Tongue is older than Latin, and that Latin has its power because it echoes Wizardry. Clearly it is an Italic tongue, with different vowel shifts; the Indo-European vocalic M became -um, not -em. (hence Expecto patronum, not patronem.)

I would believe, although I know no evidence, that Wizards used to speak it among themselves, and they have lost it as a daily speech in England because of being surrounded by English-speakers, as Irish and Yiddish are being lost.