bigot

From French bigot (“a sanctimonious person; a religious hypocrite”), from Middle French bigot, from Old French bigot, of disputed origin. It is most often believed to have derived from the identical Old French derogatory term bigot applied to the overly religious Normans, said to be known for frequently swearing Middle English bi God (“by God”) (compare Old English bī god, Middle High German bī got, Middle Dutch bi gode), which is also thought to be the origin of the surname Bigott, Bygott. (Compare the French use of "goddamns" to refer to the English in Joan of Arc's time, and les sommobiches (see son of a bitch) during World War I). From meaning "someone overly religious" it came to mean "someone overly devoted to their own religious opinion", and then to its current sense.
The French Centre National de Ressources Textuelles et Lexicales supports the Germanic origin theory above. Liberman however opines that this has "too strong a taste of a folk etymological guess invented in retrospect" and prefers Grammont et al.'s theory that it derives from Albigot (“inhabitant of Albi”), named after the commune in southern France where Catharism (also known as Albigensianism) is thought to have originated. However, neither the Oxford English Dictionary nor Online Etymology Dictionary list Grammont and Liberman's theory among their possible origins.