Flounder
My local fish market (in New England) sells something labeled "Filet of sole (flounder)." I've read the Wikipedia article about European vs North American sole, and on my last visit to the fish market I asked why he uses the terms interchangeably. He said "they're the same fish," but biologically they aren't, and I suspect "sole" just sounds a little better than "flounder." But the flounder was fresh and reportedly native, so I have no problem with it - I was just wondering whether this confusion/renaming is common.
