According to Lady Wilde in her Ancient Legends of Ireland, Oonagh is the wife of Finvarra, the king of the western fairies and of the dead. She says:Finvarra the King is still believed to rule over all the fairies of the west, and Oonagh is the Fairy Queen. Her golden hair sweeps the ground, and she is robed in silver gossamer all glittering as with diamonds, but they are dewdrops that sparkle over it.The queen is more beautiful than any woman of earth, yet Finvarra loves the mortal women best, and wiles them down to his fairy palace by the subtle charm of his fairy music.
Has anyone heard of the book "The Prophecy of the Stones", written by Flavia Bujor? In it, Oonagh is the name of a magical creature that can read people's hearts (in the context of the story, the heart is the faculty capable of emotion and thought). Oonagh is the name of a single creature and NOT a species.