Originally a pet form of John , but now a well‐established given name in its own right. It is derived from Middle English Jankin, later altered to Jackin, from Jan (a contracted form of Jehan ‘John’) + the diminutive suffix -kin. This led to the back-formation Jack, as if the name had contained the Old French diminutive suffix -in. It is sometimes also used as an informal pet form of James , perhaps influenced by the French form Jacques . It has been the most popular boys' name in England and Wales since 1995 . Well-known bearers include the actor Jack Nicholson ( b. 1937 ) and the golfer Jack Nicklaus ( b. 1940 ). See also Jock and Jake .
Dictionary of First Names © Patrick Hanks and Flavia Hodges 1990, 2003, 2006.