Ulster Scots people
Ulster Scots are an ethnic group in Ireland, descended from Lowland Scots and English from the border of those two countries, were "Border Reivers". These people first began to occupy Ireland in large numbers with the Plantation of Ulster, ordered by James I of England on land taken from the Irish nobility, mostly in the Province of Ulster. The term "Ulster-Scots" refers to both these colonists of the 17th century and, less commonly, to the Gallowglass who began to arrive from what is now northwest Scotland centuries earlier.
Ulster-Scots were largely descended from colonists from Galloway, Ayrshire, and the Scottish Borders Country, although some descend from people further north in the Scottish Lowlands and the Highlands. Ulster-Scots emigrated in significant numbers to the United States and all corners of the British Empire — Canada, Australia, New Zealand, South Africa — and to a lesser extent to Argentina and Chile in South America.
Scotch-Irish is a traditional term for Ulster Scots who later emigrated to what is now the United States; "Scots-Irish" is a more recent form of the American term, the term has usually been Scotch-Irish in America, as evident in Merriam-Webster dictionaries, where the term Scotch-Irish is recorded from 1744, while Scots-Irish is not recorded until 1972.  and is not to be confused with Irish-Scots, i.e., recent Irish immigrants to Scotland.