Sidhe

   In Celtic myth the hill people of ancient Ireland, the word being related to the Celtic name for a hill or mound. The assumption that they were the spirits of the dead appears to have crept into legend at a comparatively recent date. When the Tuatha Dé Danann were defeated by the Milesians some of them stayed behind and to each of them Dagda, who remained behind as their ruler, assigned a barrow or hill on which they appear to have buried their dead, a fact which may be the origin of the assumption that they were ghosts.