This response is known as striking the "funny bone". The name funny bone could be from a play on the words humorous and humerus, the bone on which the medial epicondyle is located, although according to the Oxford English Dictionary, it may refer to "the peculiar sensation experienced when it is struck".
The term "funny bone" describes the sensation experienced by striking the medial epicondyle, which is part of the humerus. It might originate from a wordplay involving humor and the anatomical structure of the bone.