funny bone Usually applied to the projection, the olecranon, at the back of the elbow, which is the upper end of the ulna, one of the two forearm bones. On the inner side of this is a smaller protuberance, the medial epicondyle of the humerus — the bone of the upper arm. The ulnar nerve runs in a groove on the back of the epicondyle, between this and the olecranon. The nerve can be felt and rolled under the fingers, most easily when the elbow is at a right angle, and because it is near the surface it can be painfully tweaked if the inner side of the elbow hits a hard surface. The sensation is funny only in the sense of peculiar. (Tempting though it be, there is apparently no pun intended to link it to the humerus — whose name is Latin for shoulder, referring to its upper end.)

Stuart Judge

fun·ny bone • n. inf. the part of the elbow over which the ulnar nerve passes. A knock on the funny bone may cause numbness and pain along the forearm and hand. ∎  a person's sense of humor, as located in an imaginary physical organ: photographs to jostle the mind and the funny bone.