History of the Scots language
The history of the Scots language dates from the incursion of Old English into south-eastern Scotland in the 7th century, where it gradually prevailed against Scots Gaelic. The development of Scots as a distinct language was slowed by the incorporation of Scotland into Great Britain in the 17th century, which increased the influence and prestige of English at the expense of Scots.
Source: Wikipedia — History of the Scots language (CC BY-SA 4.0)