What's a phrase you misinterpreted the meaning of for the longest time?

https://discuss.tchncs.de/post/29155606

What's a phrase you misinterpreted the meaning of for the longest time? - tchncs

I’ve seen people using “that’s what she said” in a very serious setting, as a way to say “good point/touché”. They had no idea it was from the Office.

Not a phrase, but as a kid, I thought old people got old timers, and couldn’t remember things. I later learned it was called Alzheimer’s.