This name as le Norreys (i.e. the northman) is very frequent in Irish records since the thirteenth century.  It came into special prominence with the arrival of Sir John Norris, who was responsible for the terrible massacre at Rathlin Island in 1575.  He became President of Munster in 1584 and was succeeded by his brother Thomas in 1597.  Another brother, Henry (d.1599), is favourably mentioned by the Four Masters.  The name is now found in considerable numbers in all the provinces except Connacht.  Some curious synonyms of it have been reported by local registrars, e.g. Nowry in Co. Derry, Nurse in Co. Kerry and Northbridge in west Cork.  These three names are very rare in Ireland; Nurse and Nourse are normal synonyms of Norris in England; Northridge is an English name denoting residence at the north ridge.  Bibl., Map



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.