It could be from ancient Greek, since there are ancient Greek names like Atreas, Atreides, etc. Also the fact that the person who has this name is of South American backround, makes me remember Lonko Kilapan. He is a linguistic and historian from
Chile and according to him, the tribe of Araucans in
Chile are descendants of ancient Greeks and especially of Spartans. Why don't you try to find some of his work? Sounds interesting to me...