“Hercules, it is told, after he had taken the king of Geryones from Erythea, was wandering through the country of the Celts and came to the house of Bretannus, who had a daughter called Celtine. Celtine fell in love with Hercules and hid away the kine, refusing to give them back to him unless he would first content her. Hercules was indeed very anxious to bring the kine safe home, but he was far more struck by the girl’s exceeding beauty, and consented to her wishes; and then, when the time had come round, a son called Celtus was born to them, from whom the Celtic race derived their name.”
– Parthenius, Erotica Pathemata, Celtine, 30
Gaulish Paganism 