The name Jack is of English origin and means "God Is Gracious." The origin is the culture in which the name originated, or in the case of a word--the language in which it most appears.
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. Jack White is a famous musician. The "Jack in the Box" started as a (frightening) children's toy and is now the brand of an international chain of fast food restaurants.
Jack Ruby is the famous assassin of Lee Harvey Oswald, after the latter assassinated Jack Kennedy. The most infamous Jack is likely Jack the Ripper, who murdered several women in the year 1888.
Many fictional protagonists are named Jack, including Jack Bauer from the television show, 24, Jack Pearson from This is Us, and Jack Tripper played by John Ritter, on the TV show, Three’s Company.
A jack is also a metal device used to lift an automobile in order to work on it or change a tire. In slang, when you are "jacked" you are in trouble or someone stole from you.
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