As a given name for boys, it gained some popularity in the mid-1990s after the debut of the American television series Nash Bridges. It got more exposure beginning 2005 when a character by this name started appearing on the soap opera One Life to Live.
The Cornish form of this name, Jennifer, has become popular in the English-speaking world.
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.
In America, this name received a boost of popularity in 2000 when a character bearing it began appearing on the television series The West Wing.