Thank youall so much for your help! As it ends up, it wasn't a wizard at all. The word is:
mumpsimus (MUMP-suh-muhs) noun

1. Adherence to or persistence in an erroneous use of language,
memorization, practice, belief, etc., out of habit or obstinacy.
2. A person who persists in a mistaken expression or practice.

[From a story, which perhaps originated with Erasmus, of an illiterate
priest who said mumpsimus rather than sumpsimus (1st plural perfect
indicative of Latin sumere to pick up) while reciting the liturgy, and
refused to change the word when corrected]