You bump your elbow on a table corner and — ZAP! A weird tingly shock shoots down your arm. Everyone calls it your "funny bone," but here's the thing: it's not a bone at all, and it doesn't feel very funny.

What you're actually hitting is a nerve — a long wire of living tissue that carries messages between your brain and your hand. This one's called the ulnar nerve, and it runs all the way down the inside of your arm to your pinky and ring finger.

Most nerves in your body are tucked safely inside muscle and fat, wrapped up like wires in a protective cable. But the ulnar nerve takes a risky shortcut: it runs behind your elbow in a shallow groove in the bone, with almost nothing covering it.

When you knock your elbow just right, you're squishing that exposed nerve directly against the hard bone underneath. The nerve fires off a burst of confused signals — not pain exactly, but a wild tingling buzz that zings down to your fingers.

Your brain gets this sudden flood of strange sensations from your pinky and ring finger — tingling, numbness, that electric "asleep" feeling — even though nothing actually touched your hand. The nerve is just yelling, "Something weird happened up here!"

So why call it the "funny bone" if it feels so un-funny? One theory: the bone that forms that groove is called the humerus. Humerus sounds like "humorous." Someone made a pun, and it stuck.

Another theory: "funny" used to mean "odd" or "strange" — like when something feels funny, not ha-ha funny. That tingling zap is definitely strange compared to normal touch or normal pain.

Either way, your funny bone is really just your unprotected ulnar nerve getting a surprise squeeze. The next time you whack it, you can impress everyone by saying, "Actually, it's a nerve!" Right after you stop saying "Ow ow ow ow ow."