Most people of this name in Ireland spell it as above, though occasionally the variant Grier is used; these and also Grierson are basically the same, being anglicized forms of the Scottish MacGregor, which is found unchanged in Co. Derry.  Greer is very numerous in Co. Antrim now and it occurs many times in the Hearth Money Rolls for that county (1669) and to some extent also in the rolls of other Ulster counties.  The principal families of the name came to Ireland in the seventeenth century, the earliest in the Plantation of Ulster and others a generation later.  Derry-born Samuel McCurdy Greer (1810-1880), who ended as county court judge of Cavan and Leitrim, was co-founder of the Tenant League in 1850 with Charles Gavan Duffy.



Clan From the Gaelic clann which means literally 'children'.
Mac- From the Gaelic mac, meaning 'son'
O' From the Gaelic , meaning 'grandson', 'grandchild' or 'descendant'; N is the femine form of , meaning 'daughter' or 'descendant'
Plantation (Ulster) The redistribution of escheated lands after the defeat of the Ulster Gaelic lords and the 'Flight of the Earls' in 1607.  Only counties Donegal, Derry, Tyrone, Armagh, Fermanagh and Cavan were actually 'planted', portions of land there being distributed to English and Scottish families on their lands and for the building of bawns.
Sept A family group of shared ancestry living in the same locality
Undertakers Powerful English or Scottish landowners who undertook the plantation of British settlers on the lands they were granted.
Gaelic This word in Ireland has no relation to Scotland.  As a noun it is used to denote the Irish language, as an adjective to denote native Irish as opposed to Norman or English origin.
Erenagh From the Irish Gaelic airchinneach, meaning 'hereditary steward of church lands'.  A family would hold the ecclesiastical office and the right to the church or monastery lands, the incumbent at any one time being the erenagh.