791: Celtic Languages Feb 6, 2017

Through the first millennium BCE, Celtic languages were some of the most widely spoken throughout Europe from the Iberian Peninsula to Asia Minor. As time went on, with the movement of the Romans, Germanic tribes, and groups from the east, Celtic languages faded out of use. Now, there are only six Celtic languages, two of which were dead and only brought back after various revitalization efforts: Manx and Cornish, the others being Scots and Irish Gaelic, Welsh, and Breton. The only modernly spoken Celtic language spoken natively outside of the British Isles is Breton spoken in Brittany. Unfortunately, this is not an official language of France, and most of the speakers who use it are over sixty-five. In fact, Welsh is the only Celtic language not classified as endangered.
See more on lost languages here.