The word elfdalian seems to have been coined by J.R.R. Tolkein in Lord of the Rings. Is it a dialect spoken by elves? A legend told throughout Middle Earth? A term of endearment?
Actually, Elfdalian is a language. However, it’s not spoken by Elves, but by a forest community of around 2,500 people in central Sweden around the isolated city of Älvdalan. Interestingly, Elfdalian ( a word created in Swedish and meaning “river valley”) is not close to any Scandinavian language (Swedish, Norwegian, Danish, Finnish), but rather to Old Norse, spoken by the Vikings in ancient times. It is almost a fossil language, and of great interest to language historians.
For more information, read this article in an English language Swedish website.