Ah, Rhu--dear bel was right in her assesment -- and i hope Dr Bill (or an other of our doc's) will fill in the details (and you where too!)

there is a nerve the runs on the out side of bone-- (from the humerus to the (radia? unla?) at the point of the elbow. (it is rare for major nerves to run so close to the skin,) if you bump your elbow at the point where the nerve is closest to the skin- you experience a sharp unusual pain-- you have bumped your "funny bone" --

I don't think the play on Humerus/humorous is known by most-- but every culture has noticed the special reaction that occurs when you bump just the (wrong) right spot on your elbow.--even ones that don't use our latin names for bones!