Fun fact: there's a test you can do called wordsum which correlates extremely highly, like .71, to IQ. It's just asking you 10 vocabulary questions. It turns out knowing advanced vocabulary correlates really well to IQ.
I don't know if I can get behind .71 implying "correlates really well" ... that's the issue I had recently with talking with GPT, it was evaluating my logical reasoning ability based on the vocabulary I was employing. You don't need fancy words to be intelligent.