Jenna is a diminutive of Jennifer. Jennifer is ultimately derived from Guinevere. Guinevere originates in Welsh language and means "woman of white magic". This was the name of a legendary character in Arthurian legends. She was the wife of King Arthur and a lover of Sir Lancelot, Arthur's chief knight. Throughout history, Guinevere was an inspiration for many plays, songs and films. As a feminine given name Jennifer has been used in the English-speaking countries since the 20th century and nowadays is one of the most popular given names in the United States.