http://www.etymonline.com/index.php?term=caste
As you see the idea of the world Caste being used as a term to define race or level in society is rather late, mid 1500's and on. So unless the area of Whitecast was named later, its not likely to mean race. I thought this area was in Brittania, there weren't not Roman gypsies there, right?
Sorry, I confuse easily ^_^