This name was fairly common in France, England and the United States in the early 20th century. It became quite popular in France and England at the end of the 20th century, just when it was at a low point in the United States. It quickly climbed the American charts and entered the top ten in 2014.
Originally more common as a name for boys in America, it became more popular for girls in the 1960s. It began rapidly increasing after 1973, possibly due to a character (played by Natalie Wood) in the television movie The Affair. It reached an apex in the United States ranked 17th in 1990, though it has quickly fallen away since then.
This name has been used in the English-speaking world since the Protestant Reformation. In America it received a boost in popularity after the birth of Esther Cleveland (1893-1980), the daughter of President Grover Cleveland [1].
The name was popular in France during the Middle Ages (the more common French form is Gisèle). Though it became known in the English-speaking world due to Adolphe Adam's ballet Giselle (1841), it was not regularly used until the 20th century.
The Cornish form of this name, Jennifer, has become popular in the English-speaking world.
Although this name was used by Jews in the Middle Ages, it was not typical as an English Christian name until after the Protestant Reformation, being common among the Puritans.