Irish was brought to Scotland by the migration of Fergus Mor from Antrim to Argyll about CE 500.

It spread rapidly throughout the Highlands and Lowlands replacing Celtic Pictish and, later, Cumbric north of the border. From the 12 century, Scottish Gaelic became recognisably different from Irish.

The replacement of Celtic Pictish and Cumbrian was accompanied by a bi-lingual period. Many Gaelic place-names are translations of British terms and this process, when incomplete, shows that the speakers were familiar with meaning of the terms used in both languages.