I cannot believe you guys. I'm sorry, this is just amazing.
"bianco" means "white"
"corona" in Corona Mountain probably means that it's the highest point on the island, because the word "corona" is where we get our word "crown"
As for Il Piantissimo, Sapph is at least in the ballpark. It's something probably like "the real Pianta-ish guy" because -issimo is simply an intensifier of what would logically be "pianto," but isn't.
Also, Vid is right about Nokis.
Isle Delfino is based on Italy, and that should be obvious if not from anything but the insane amount of Italian words everywhere.