From the Norman French form of the Welsh name Gwenhwyfar, composed of the elements gwen meaning "fair, white" and hwyfar meaning "smooth". In Arthurian legend she was the beautiful wife of King Arthur who engaged in an adulterous affair with Sir Lancelot. Her betrayal of her husband with Mordred prompted the battle of Camlann, which led to the deaths of both Mordred and Arthur.

The Cornish form of this name, Jennifer, has become popular in the English-speaking world.