Which language spoken by a very small community in Scotland is considered the most northern of the Celtic languages and had to be rescued from extinction in the 20th century by a conscious educational effort?

Scottish Gaelic (Gàidhlig), spoken mainly in the Highlands and Islands of Scotland, is the northernmost Celtic language. It suffered serious decline after the Battle of Culloden (1746) and the 'Highland Clearances'. In the 20th century, thanks to the creation of immersion schools (such as those on the Isle of Skye), media in Gaelic and official recognition, its decline has been slowed, although it remains a threatened language with around 60,000 speakers.