I only realized recently that the English word "diva" comes from the Latin diva.
The way I realized was that I was talking to my roommate about my cat Fia and what a "diva" she is (she really is, too; she would have made a perfect stand-in for Bastet back in Egyptian days...) Just then my other cat, Rumi, walked by, and my roommate looked at him and said something like, "Awww, you're a diva too, aren't you?"
"He would need to be a divus, though," I automatically thought, which was when it dawned on me.
I only realized quite recently (maybe two months ago) that the first part of the word "cosplay" was short for "costume".
I think it's because, for whatever reason, I pronounced it "coze-play" in my head, which sent me down the wrong track by making me think of "clothes", which has all the right letters in it and in the right order (though not adjacent to one another).