Word Origins writes that the term commonly used for a cramp or pulled muscle “…gained widespread use in baseball jargon.” The first known use of the term was in the Boston Globe on July 17, 1886. It said baseball player Joe Quest had used the term to describe pains being suffered by other players. It is possible, although not confirmed, that the term originated when Quest was working as an apprentice in a machine shop.  There was an old horse named Charlie that walked as if his legs were stiff while pulling the delivery loads from the shop. Quest supposedly came up with the term “Charley horse” for anyone experiencing pain in their legs.