crazy bone

plural crazy bones

1. The funny bone; the ulnar nerve in the elbow.

   My hand was at his elbow, my fingers just at the indentation of his elbow, just about where you bump the nerve point everyone calls the “crazy-bone”.

   2008, Thomas S. Purtell, Natural Martial Arts, page 34

   1 more example

   I have seen a person in England, who had touched a torpedo; and he said the shock it gave him, was like striking that tender part of the elbow, which we call the crazy bone, very hard indeed;

   1830, Mrs. John Farrar, The Children's Robinson Crusoe, page 318