Irish belongs to the northern group of Celtic languages known as Goidelic or Q-Celtic. It is closely related to Manx and Scottish Gaelic, with which it retains a degree of mutual intelligibility depending on the user and the medium. The language has been spoken in Ireland, including in Holywood, for at least three millennia; it was the dominant means of communication until the seventeenth century and is the source of most local place-names.
North Down was settled as part of the Hamilton-Montgomery Plantation of 1606, with Holywood becoming part of the lands of James Hamilton. In addition to the substantial numbers of migrants from the south-west of Scotland, where Gaelic was recessive, many of the incomers originated in Arran, Kintyre, Islay, Jura, Mull and Argyll, all areas where the language is either still spoken today or was present until relatively recently. Gaelic-speakers from Scotland would have had no difficulty communicating with Irish counterparts at the time. As late as 1873, J. A. H. Murray, later to become founding editor of the Oxford English Dictionary, was able to quote his correspondent Robert Shipboy MacAdam in support of the “absolute identity” of the vernacular of eastern Ulster and Arran.
Although Gaelic-speakers were a minority of Planters, the vast majority, if not all, would have had Gaelic-speaking forebears, in some cases only one or two generations previously. The Scots poet Robert Burns celebrates the Gaelic heritage of his native Ayrshire in his poem ‘The Vision’, and loan words such as greeshoch and ingle would already have been present in the speech of the new arrivals.