Rhodes: nothing to do with the Mediterranean island, just a fancy spelling of Old English ROD, meaning "cleared land", the ancestor of our modern word, road. I have read that this is a Yorkshire name, though I haven't been able to confirm this.
Ivory: from a French place name, Ivry-la-Bataille. There may be other origins, but I'm certain that this is the chief, if not the only one.
McCrystal: son of Crystal, a Lowland Scots diminutive of Christopher. Also found in Northern Ireland since the 17th century.
Scwonberg: looks like a German or Austrian place name; berg means "mountain".