One of my favorite things about the English language is how many perfectly innocent-sounding words are a little bit less wholesome than you might expect.
Take the word “gym,” for instance—that’s gym as in gymnasium, the place where you go to work out, train or play sports. Gymnasium is a Latin word, and originally comes from the Greek gymnasion.
As you probably know, the ancient Greeks were big into sports—and the sexy strong people who played them. To more effectively show off that physicality, in the Olympics and other competitions, the athletes performed in the nude—except of course for the olive oil they rubbed all over themselves to more attractively gleam.
Which is why the Greek word gymnasion, and by extension today’s English words gym and gymnasium, literally mean “a place to train naked.” The base word gymnos means “naked.”
But of course the gymnasium wasn’t just about sexy bods—it was also about sexy minds, which is why in Greek and Latin a gymnasium was also a name for a school—presumably one to which most people wore clothes. It remains a word for a high school or K-12 school in many European countries today.
Useless Etymology 