IrishCentral has put together a list of the top 100 common Irish surnames with a little explanation of where these names come from.
From Aherne to Whelan here is our top 100 Irish names:
Aherne - (Ó hEachtighearna/Ó hEachthairn) (each, steed tightearna, lord): Originally Dalcassian, this sept migrated from east Clare to Co. Cork. In County Waterford the English name Hearn is a synonym of Hearn.
MacAleese - MacGiolla (son of the devotee of Jesus): The name of a prominent Derry sept. There are many variants of the name such as MacIliese, MacLeese, MacLice, MacLise, etc. The best known of this spelling, the painter Daniel MacLise, was a family of the Scottish highlands, know as MacLeish, which settled in Cork.
Allen: This is usually of Scottish or English origin but sometimes Ó hAillín in Offaly and Tipperary has been anglicized Allen as well as Hallion. Occasionally also in Co. Tipperary. Allen is found as a synonym of Hallinan. As Alleyn it occurs frequently in mediaeval Anglo Irish records. The English name Allen is derived from that of a Welsh saint.
MacAteer - Mac an tSaoir (saor, craftsman): An Ulster name for which the Scottish MacIntyre, of similar derivation, is widely substituted. Ballymacateer is a place-name in Co. Armagh, which is its homeland. Mac an tSaoir is sometimes anglicized Wright in Fermanagh.
MacAuley - Awley: There are two distinct septs of this name, viz. MacAmhalghaidh of Offaly and West Meath, and the more numerous MacAmhlaoibh, a branch of the MacGuires which as MacAmhlaoibh gives the form Gawley in Connacht. Both are derived from personal names. The latter must not be confused with MacAuliffe.
MacAuliffe - Mac Amhlaoibh: An important branch of the McCarthys whose chief was seated at Castle MacAuliffe. The name is almost peculiar to south-west Munster.
Barry - de Barra: The majority of these names are of Norman origin, i.e. de Barr (a place in Wales); they became completely hibernicized. Though still more numerous in Munster than elsewhere the name is widespread throughout Ireland. Barry is also the anglicized form of Ó Báire (see under Barr) and Ó Beargha (meaning spear-like according to Woulfe) a small sept of Co. Limerick.
Blake - deBláca (more correctly le Bláca): One of the ‘Tribes of Galway’ an epithet name meaning black which superseded the original Cadell. They are descended from Richard Caddell, Sheriff of Connacht in 1303. They became and long remained very extensive landowners in Co. Galway. Branch settled in Co. Kildare where their name is perpetuated in three town lands called Blakestown.
Brennan - Ó Braonáin (The word braon has several meanings, possibly sorrow in this case): The name of four unrelated septs, located in Ossory, east Galway, Kerry and Westmeath. The county Fermanagh sept of Ó Branáin was also anglicized Brennan as well as Brannan.
O’Brien - Ó Briain: A Dalcassian sept, deriving its name from historical importance from the family of King Brian Boru. Now very numerous in other provinces as well as Munster, being the fifth most numerous name in Ireland. In some cases O’Brien has been made a synonym of O’Byrne and others of the Norman Bryan.
Browne - De Brún: more correctly le Brún (brown). One of the Tribes of Galway. Other important families of Browne were established in Ireland from the Anglo-Norman invasion onwards. The Browns of Killarney, who came in the sixteenth century, intermarried with the leading Irish families and were noted for their survival as extensive Catholic landowners throughout the period of the Penal Laws (The Kenmare associated with their name is in Co. Limerick) The Browne family shown on the map in Co. Limerick is of Camus and of earlier introduction. Yet another important family of the name was of the Neale, Co. Mayo. In that county Browne has also been used as a synonym of (O) Bruen.
Burk - de Burgh de Búrca: This one of the most important and most numerous Hiberno-Norman names. First identified with Connacht it is now numerous in all the provinces (least in Ulster). Many sub-septs of it were formed called MacHugo, MacGibbon, Mac Seoinín (Jennings), MacRedmond, etc.
Butler: Always called deBuitléir in Irish, though it is of course properly le Butler not de. It is one of the great Norman-Anglo which, however, did not soon become hibernicized like the Burkes, etc. Historically it is mainly identified with the Ormond country. It is now very numerous in all the provinces except Ulster.