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.
Gaulish language
Gaulish was an ancient Celtic language that was spoken in parts of Europe before and during the period of the Roman Empire. In the narrow sense, Gaulish was the language spoken by the Celtic inhabitants of Gaul (modern-day France, Luxembourg, Belgium, most of Switzerland, Northern Italy, as well as the parts of the Netherlands and Germany on the west bank of the Rhine). In a wider sense, it also comprises varieties of Celtic that were spoken across much of central Europe ("Noric"), parts of the Balkans, and Asia Minor ("Galatian"), which are thought to have been closely related. The more divergent Lepontic of Northern Italy has also sometimes been subsumed under Gaulish.