I got an e-mail from a friend today talking about "ribbing" me. I wondered how "rib" came to mean to tease. I checked both World Wide Words and Word Detective, and it wasn't there. When I looked it up in the dictionary, it talked about "ribbing" being used informally, but there was no indication of why. Does anyone know?

I'm guessing but could it be from "rib-tickling"?

Maybe it's because of the practice of some people to dig you in the ribs to get their point across?

A rib-tickler to make sure you understand their point of view.. a less violent 2x4 to the body...

Perhaps that's it, but I wish I could find some background for it. I suppose informal words or slang don't really have etymology.