Mahomet, Mahommé, Mahommes, Mahommet
In the Vulgate Estoire del Saint Graal, Mohammed is one of four gods worshipped by the pagans in Britain, before they are converted to Christianity by Joseph of Arimathea.
The other three gods were Jupiter, Apollo, and Tervagant.
Sources
Vulgate Lancelot | 1215-1230
Vulgate Estoire del Saint Graal | 1220-1235