Goidelic languages were once the most prominent by far among the Scottish population, but now are restricted to the West.
From the en.wikipedia.org
Goidelic languages historically formed a dialect continuum stretching from the south of Ireland through the Isle of Man to the north of Scotland.
From the en.wikipedia.org
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Gaelic: any of several related languages of the Celts in Ireland and Scotland
The Goidelic languages are one of the two branches of the Insular Celtic languages, the other consisting of the Brythonic languages. Goidelic languages historically formed a dialect continuum stretching from the south of Ireland through the Isle of Man to the north of Scotland. ...
Of or relating to the Gaels, particularly their language, in antiquarian contexts
The earlier language of Ireland: its descendants being Modern Irish, Scottish Gaelic and Manx.