What did the snow elves call Skyrim? Do we actually know?
According to the pocket guide to the empire; "Exactly when the Nords first crossed the ice-choked Sea of Ghosts from Atmora, their original homeland, is uncertain. These first settlers named the land "Mereth", after the Elves that roamed the untamed wilderness which then covered the whole of Tamriel."
Of course this book is biased, because on the snow elves eusp wiki it says they had a civilization that "even rivaled the altmer of the summerset isles".
My best guess (nerd theory alert) is that before they were overthrown, the Nords called the land Mereth and the snelves called the land "Old Kingdom" (from eusp) or something else unknown, then the nords just decided to throw all that out for some reason and call the land "Skyrim" because of Kyne (because why not) (or maybe something else?)