History of Scottish Gaelic
All surviving dialects are Highland and/or Hebridean dialects. Dialects of Lowland Gaelic have become defunct since the demise of Galwegian Gaelic, originally spoken in Galloway, which seems to have been the last Lowland dialect and which survived into the Modern Period. By the 18th century Lowland Gaelic had been largely replaced by Lowland Scots across much of Lowland Scotland. According to a reference in "The Carrick Covenanters " by James Crichton, the last place in the Lowlands where Scottish Gaelic was still spoken was the village of Barr in Carrick: only a few miles inland to the east of Girvan, but at one time very isolated. Crichton gives neither date nor details.
Gallaecian language
Gallaecian, or Northwestern Hispano-Celtic, is an extinct Celtic language and was one of the Hispano-Celtic languages. It was spoken at the beginning of the 1st millennium in the northwest corner of the Iberian Peninsula that became the Roman province of Gallaecia and is now divided between the modern regions of Galicia, Norte Region, Portugal, western Asturias, and the Province of León, in Spain.