The Collaborative International Dictionary of English v.0.48:
Arawn \Arawn\ prop. n. (Welsh mythology) Lord of Annwfn (the other world; land of fairies). [WordNet 1.5]WordNet (r) 3.0 (2006):
Arawn n 1: Celtic deity who was the lord of Annwfn (the other world or the land of fairies)