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The Origin of Irish Family Names

It is a help when tracing your family history to know something about the origin of and evolution of Irish names and particularly how names have changed over the centuries.

Early times: In ancient Ireland the population was much smaller than today and the mass movement of people was uncommon. It was usual therefore for a person to be known only by one name: Niall, Eoin, Art, etc. Once there was no one else in the locality with the same name then this was not a problem.

The Gaelic Clann system was well established and this gave people a common identity with their people of the tribe and with the commonly shared area. This single name system began to break down during the eleventh century as the population was growing and there was a need for a further means of identification. The solution was to adopt a prefix such as Mac (Mc is an abreviation) or Ó. Mac means 'son of' whilst Ó means 'grandson of'. Mac surnames are generally of a much later date than Ó. The vast majority of Gaelic Irish surnames were created during the eleventh and twelfth centuries.

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It should be noted that the Scottish Gaels were actually descendants of Gaelic emigrants to Scotland. The word 'Scotus' is Latin for 'Irishman'. Scottish settlers who moved to Ireland (and especially Ulster) may already have been of Gaelic Irish descent.

Septs: The Clans eventually broke up into a number of distinct septs or groups. These groups were headed by an original member of the clan and dominated a particular part of the countryside. It was not uncommon for septs from the same clan to be found in completely different parts of the country (O'Connor for example) so it is important when researching your roots to try to find out the original part of the country that your ancestors came from as this may be a completely different area from that where the 'major' sept was domicile.

The sept system was an integral part of Gaelic society and survived and was even propagated by the Norman invaders. The system did not survive the English invasion and colonisation of the seventeenth century however, and it became a disadvantage to have a Gaelic sounding name.

Anglicization: The Penal laws that were enforced by the colonists attempted to completely subjugate the Gaelic way of life. It is about this time then, that many Gaelic names changed to their Anglo equivalent or translation. This can cause confusion as many of the names were misinterpreted or misspelled. The name McEaneny for example has a number of variants including McAneny and Bird (the Irish word for bird is éan). Mac an Thomáis was converted to Holmes, Mac Giolla Íosa to MacAleese, etc. The conversion of names beginning with Mac and Mc was even more difficult because the removal of the M sound from the name often completely changed the sound of the name.

The revival of Gaelic consciousness in the later eighteen hundreds saw many Irish families reassume the Mac, Mc, Ó or other Irish form of their names although this was reduced in a number of cases depending on the sound of the name (Kelly is still much more prevalent than O'Kelly, Murphy more prevalent than O'Murphy, etc.)

Surnames today: There are many different origins for Irish names today but the vast majority can be broken down into either of three categories: Gaelic Irish, Cambro-Norman, and finally Anglo-Irish.

The Table below gives a listing of the 100 most commonly names found in Ireland and their meanings. These details were compiled from the 1890 Matheson report.

RankNameGaelic EquivalentMeaningCoat of Arms
1 MurphyÓ Murchadhasea-battlerClick Here
 2 Kelly  Ó Ceallaighbright-headedClick Here
 3 O'Sullivan  Ó Súilleabháin  dark-eyedClick Here
 4 Walsh  Breathnach   WelshmanClick Here
 5 Smith  Mac Gabhann  son of the smith Click Here 
 6 O'Brien  Ó Briain   high, nobleClick Here
 7 Byrne   Ó Broin   a ravenClick Here
 8 Ryan   Ó Maoilriain   kingClick Here
 9 O'Connor  Ó Conchobhair  patron of warriorsClick Here
 10 O'Neill  Ó Néill  from Niall of
the Nine Hostages
Click Here
 11 O'Reilly  Ó Raghallaigh Click Here
 12 Doyle   Ó Dubhghaill   dark foreignerClick Here
 13 McCarthy Mac Carthaigh  loving personClick Here
 14 Gallagher Ó Gallchobhair  lover of foreignersClick Here
 15 O'Doherty  Ó Dochartaigh   hurtfulClick Here
 16 Kennedy  Ó Cinnéide   helmet headedClick Here
 17 Lynch   Ó Loinsigh   seafarer, exileClick Here
 18 Murray  Ó Muireadhaigh  lord, masterClick Here
 19 Quinn   Ó Cuinn   wisdom, chiefClick Here
 20 Moore  Ó Mordha   majesticClick Here
 21 McLoughlin  Mac Lochlainn vikingClick Here
 22 O'Carroll  Ó Cearbhaill   valorous in battleClick Here
 23 Connolly  Ó Conghaile   fierce as a houndClick Here
 24 Daly   Ó Dálaigh assembles frequentlyClick Here
 25 O'Connell  Ó Conaill   strong as a wolfClick Here
 26 Wilson  Mac Liam   son of WilliamClick Here 
 27 Dunne   Ó Duinn  brownClick Here
 28 Brennan  Ó Braonáin   sorrow Click Here
 29 Burke   de Búrca   from Richard de BurghClick Here
 30 Collins  Ó Coileáin   young warrior Click Here
 31 Campbell    crooked mouth Click Here
 32 Clarke   ÓCléirigh   clergyman Click Here
 33 Johnston  Mac Seáin   son of JohnClick Here
 34 Hughes  Ó hAodha   fireClick Here
 35 O'Farrell  Ó Fearghail   man of valourClick Here
 36 Fitzgerald  Mac Gearailt   spear ruleClick Here
 37 Brown   Mac an Bhreithiún  son of the brehon (judge)Click Here
 38 Martin Mac Giolla Mháirtín  devotee of Saint Martin Click Here
 39 Maguire Mag Uidhir   dun-coloured Click Here
 40 Nolan   Ó Nualláin   famousClick Here
 41 Flynn   Ó Floinn   bright redClick Here
 42 Thompson  Mac Tomáis   son of ThomClick Here
 43 O'Callaghan Ó Ceallacháin   bright headedClick Here
 44 O'Donnell  Ó Domhnaill   world-mighty Click Here
 45 Duffy   Ó Dufaigh   dark, blackClick Here
 46 O'Mahony  Ó Mathúna  bear-calfClick Here
 47 Boyle   Ó Baoill  vain pledgeClick Here
 48 Healy   Ó hÉalaighthe   artistic, scientificClick Here
 49 O'Shea  Ó Séaghdha   fine, stately Click Here
 50 White   Mac Giolla Bháin  of fair complexionClick Here
 51 Sweeney  Mac Suibhne   pleasant Click Here
 52 Hayes   Ó hAodha   fireClick Here
 53 Kavanagh  Caomhánach   comely, mildClick Here
 54 Power   de Paor  the poor manClick Here
 55 McGrath  Mac Craith  son of graceClick Here
 56 Moran   Ó Móráin   greatClick Here
 57 Brady   Mac Brádaigh   spiritedClick Here
 58 Stewart  Stiobhard   one who superintendsClick Here
 59 Casey   Ó Cathasaigh  vigilant in war, watchfulClick Here
 60 Foley   Ó Foghladh   a plundererClick Here
 61 Fitzpatrick  Mac Giolla Phádraig  devotee of Saint Patrick Click Here
 62 O'Leary Ó Laoghaire   calf-herdClick Here
 63 McDonnell  Mac Domhnaill  world-mightyClick Here
 64 MacMahon  Mac Mathúna  bear-calfClick Here
 65 Donnelly  Ó Donnghaile   brown valourClick Here
 66 Regan   Ó Riagáin   little kingClick Here
 67 Donovan  Ó Donnabháin  brown, blackClick Here
 68 Burns     from Scottish BurnessClick Here
 69 Flanagan  Ó Flannagáin   red, ruddy Click Here
 70 Mullan  Ó Maoláin   baldClick Here
 71 Barry   de Barra   Cambro-Norman nameClick Here
 72 Kane  Ó Catháin   battlerClick Here
 73 Robinson     son of RobertClick Here
 74 Cunningham     Scottish nameClick Here
 75 Griffin  Ó Gríofa   Welsh: GruffuddClick Here
 76 Kenny   Ó Cionaoith   fire sprungClick Here
 77 Sheehan  O'Siodhachain   peacefulClick Here
 78 Ward   Mac an Bhaird  son of the bardClick Here
 79 Whelan  Ó Faoláin   wolfClick Here
 80 Lyons   Ó Laighin   greyClick Here
 81 Reid     red haired,
ruddy complexion
Click Here
 82 Graham     grey homeClick Here
 83 Higgins  Ó hUiginn Click Here
 84 Cullen   Ó Cuilinn   hollyClick Here
 85 Keane   Mac Catháin Click Here
 86 King   Ó Cionga Click Here
 87 Maher   Meagher   fine, majestic Click Here
 88 MacKenna  Mac Cionaoith  fire-sprungClick Here
 89 Bell   Mac Giolla Mhaoil Click Here
 90 Scott    a Scottish gaelClick Here
 91 Hogan   Ó hÓgáin   youngClick Here
 92 O'Keeffe  Ó Caoimh   gentleClick Here
 93 Magee   Mag Aoidh   fire Click Here
 94 MacNamara  Mac Conmara   hound of the sea Click Here
 95 MacDonald  Mac Dónaill   world-mightyClick Here
 96 MacDermott  Mac Diarmada  free from jealousyClick Here
 97 Molony  Ó Maolomhnaigh servant of the Church Click Here
 98 O'Rourke  Ó Ruairc  Click Here
 99 Buckley  Ó Buachalla   cow herdClick Here
 100 O'Dwyer Ó Dubhuir   black Click Here

Where to Next?
Clicking Here to find out about our Irish Genealogy Starter Guide

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The Origin of Irish Family Names