The name Jack is primarily a male name of English origin that means God Is Gracious.Originally a nickname for the given name John, it has now become a given name on its own. When short for Jackson, the name Jack it means Son of Jack/John. Nicknames of the name Jack include Jay and J.J. Jac and Jak are alternate spellings of the name Jack.Famous Jacks tend to actually have the first name John, such as President John Fitzgerald Kennedy. Jack Nicholson is a famous actor, not to be confused with Jack Niklaus, the golfer. Jack Benny was a famous comedian and Jack Black is both a comedian and actor. Jack Dempsey was a famous boxer.