From The Art and Popular Culture Encyclopedia
In the Gaulish language, the word Dusios referred to a deity (deus) among the continental Celts who was identified with the god Pan of ancient Greek religion and with the gods Faunus, Inuus, Silvanus, and Incubus of ancient Roman religion. Like these deities, he might be seen as multiple in nature, and referred to in the plural (dusioi or Latin dusii). Although the Celtic Dusios is not described in late-antique sources independently of Greek and Roman deities, the common functionality of the others lay in their ability to impregnate animals and women, often by surprise or force. Dusii continue to play a role in the magico-religious belief systems of Gaul and Francia as a type of incubus in early-medieval paganism and Christianity.
Discursive treatment of this group of beings, including the dusii, with remarks on the meaning of "fig," in Richard Payne Knight's "On the Worship of the Generative Powers During the Middle Ages of Western Europe" in Two Essays on the Worship of Priapus (London, 1865).