What is one word you realized you were pronouncing wrong until you heard someone else say it?

Mine: affidavit

Pronounced it a-fit-a-vit (not unlike "a Fitbit") for about 3 months in college trying to get out of a dorm contract I wasn't happy with.

Nitter

I'm dyslexic so my relationship to words like "affidavit" is a strange one. My first exposure to the word must have been via a tv series. I watched an insane amout of tv as a kid. So I heard the word many years before I ever saw the written form. With such words - there's confusion in my mind when I see the written form. If I were to look at the word and try to pronounce it - I'd likely mispronounce it like then I was a kid coping with pretty easy words that still gave me grief.