In most pagan religions, supernatural forces are associated with animals, the five elements and the Goddess. Sometimes the fairies were called Goddesses themselves. In several folk ballads the Fairy Queen is addressed as ‘Queen of Heaven.’ Welsh fairies were known as ‘the Mother’s Blessing.’ Breton peasants called the fairies Godmothers.
In Gaul (France and Belgium), Hispania (Spain) and Britannia (Britain), the pagan deities that were worshiped before the Roman invasion were gradually reduced to the status of fairies in mythology and folklore when Christianity spread to the west and north.
Many of the Irish tales of the Tuatha Dé Danann refer to these beings as fairies, though in more ancient times they were regarded as Goddesses and Gods or a race of fair people. They looked very much like human, in size and shape, except that they have special magical powers and seemed eternally young.
The Tuatha Dé Danann were spoken of as having come from Islands in the north of the world, or, in other sources, from the sky. After being defeated in a series of battles with other Otherworldly beings, and then by the ancestors of the current Irish people, they were said to have withdrawn to the sídhe (fairy mounds), where they lived on in popular imagination as “fairies.”
Similar degeneration occurred with the Welsh y Mamau (‘the Mothers’) in Wales, but also in Scotland and other surviving pockets of Celtic kingdoms (such as Cornwall, Brittany and island of Man).