Fun with Words

So I was thinking about how something in my last facebook status post sounded off, and upon identifying it, I became curious. I should have said “since Drew Barrymore was IN E.T” and not “on.” Saying on was making me think of Entertainment Tonight, not the movie.

Have you noticed that we tend to say an actor is “in” a movie, but “on” a TV show? Why is that? From whence did it develop?

Linguistics friends, I expect answers!