This was the name of several dukes of Brittany, and Breton settlers introduced it to England after the Norman Conquest. Famous modern bearers include Alan Shepard (1923-1998), the first American in space and the fifth man to walk on the moon, and Alan Turing (1912-1954), a British mathematician and computer scientist.
American writers Jack London (1876-1916) and Jack Kerouac (1922-1969) were two famous bearers of this name. It is also borne by the actor Jack Nicholson (1937-) and the golfer Jack Nicklaus (1940-). Apart from Nicklaus, none of these famous bearers were given the name Jack at birth.
In the United Kingdom this form has been bestowed more frequently than John since the 1990s, being the most popular name for boys from 1996 to 2008.
Its modern use as a feminine name may have been influenced by the British-American author Taylor Caldwell (1900-1985). Since 1990 it has been more popular for girls in the United States. Other England-speaking regions have followed suit, with the exception of England and Wales where it is still slightly more popular for boys. Its popularity peaked in America the mid-1990s for both genders, ranked sixth for girls and 51st for boys. A famous bearer is the American musician Taylor Swift (1989-).