I think it stands for the Skin of Poison. I believe Snake and Spider represent Poison Resistance.
I think Ordos is mentioned breifly in the books and Westwood Studios added them into Dune 2 for the sake of the game. The first Dune game was far better though. House Atredies is actually from the planet Calladan, a very wet planet. House Harkonnen are from, at a forgotten guess, Grimera Prime, a hostile mountainous world. Can anyone confirm this?
