Irish Surnames of Gaelic Origin

Gaelic Surnames in Ireland

These are the oldest names in Ireland and often reflect the clan and territorial system that prevailed in the Celtic era.

Gaelic names fall mainly into four broad groups:

1. Names referencing an ancestor

Examples include O Toole (Ó Tuathail) meaning “descendents of Tuathal”, who was a 10th century King of Leinster.

The name does not always refer to a specific known character, so while MacCormack (MacCormac) means “son of Cormac”, there is no single Cormac to whom all can trace their ancestry.

2. Names deriving from a place

Two examples, from many, are McNulty (Mac An Ultaigh) which means “Son of Ulster” and Delaney (Ó Dubhshlaine) meaning “of the black river Slaney”.

Conversely a huge number of Irish place names are derived from the names of people who lived in or ruled over them.

3. Names relating to work or a profession

O Leary (O Laoghaire) means “descendant of the calf keeper” and Guinness (MacAonghusa) means “son of the healer”. There are many more.

4. Names based on personal characteristics

Reilly (Ó Raghailligh) means “of the gregarious people” and Lawlor (O’Leathlobhair) means “half leper” while, somewhat unkindly, Kennedy (Ó Cinneide) means “of the ugly head”.

Sons and Grandsons

The commonly found “Mc” (or  “Mac”) before an Irish name means “Son of”, while the even more frequent “O'” means “grandson of”.

So MacAuley means “son of Auley”, and O’Keefe (O Caoinmh) means “grandson of Caoinmh”. Both can be interpreted as meaning “descendent of”.

These names are not always related to a specific known person in the past, or even to a person at all. Thus O’Grady (Ó Grádaigh) means “descendent of the illustrious”, McGill (Mac An Ghaill) “descendent of the foreigner” and, interestingly, MacTaggart (Mac antSagart) means “son of the priest”. Mmm.

Daughters and Wives

Obviously daughters cannot be “son of” or “grandson of” anybody, and so female members of a family will have before their names “Ní” or “Níc”, which comes from from Iníon Mhic meaning “daughter of the son of”.

For example my name in Irish is Cait Nuaillain (“Katherine, daughter of the son of the noble man”), but my brother is Seamus Ó Nuaillain (“James, grandson of the noble man”). Sadly our nobility is in name only.

As in many language, things change with female names when marriages occur.

If Mary marries Sean Ó Doinn, and takes his name, she becomes Mary Bean Uí Doinn, which literally means “Mary, wife of the grandson of Doinn”. Had she married Padraig MacCarthaigh she would have been Mary Bean MhicCarthaigh or “Mary, wife of the son of Carthaigh”.

The ‘bean’ part, which means ‘wife’ is often dropped in comman useage, giving Mary Doinn orMary MhicCarthaigh

But even though it is not the same as her husband’s, her married status would be quite clear from her name, .

The Anglicisation of Gaelic Names

During the 18th and 19th centuries there were concerted efforts by the English to suppress the use of the Irish Language and the use of Irish names. At that time falling in line and changing your name to something with a more English sound was a pragmatic move which improved your chances of social and economic advancement.

This had two primary effects on Irish names:

  1. The use of Mac and O’ was dropped by many families
    Some families have since revived the O or Mac, others never did, which explains why you will find Mahony and O’Mahony, Neill and O’Neill, all with a common history.
  2. Old Gaelic names became anglicised in different ways
    Sometimes the anglicised version was a translation, sometimes it was a phonetic spelling of the Irish,  sometimes it was a mixture of the two.

The latter change in particular can cause great confusion to those researching names, as there can be many very different versions in English of a single original Gaelic name and conversely multiple Irish versions of an English surname.

Paul Hewson, photo by Phil Romans

Paul Hewson, photo by Phil Romans

Take the name MacAoda, which can mean either “son of Aodh” or “son of Hugh”, since Aodh is the Irish version of the given name Hugh.

Depending on where in Ireland you lived, and thus on the regional version of the Irish language you spoke, Aodh would be pronounced either as “ee”  in the word ‘see’ or as “ay”  in the word ‘say’.

This led to huge variation in the way the name was changed into English.

All of these could derive from MacAodh: Magee, MacKee, McKee, MacCoyMacKay, McCay, Hughes, McHugh, Hayes and Hewson.

The last name there may be familiar – Bono of Irish band U2 is properly known as Paul Hewson, and in Irish would be Pól MacAoda.

Distribution of Gaelic Names

Most names of Gaelic origin are widely distributed in Ireland, and indeed elsewhere, but it is remarkable how closely some families have remained to the places where their names originated, often more than a thousand years ago.

For example the name Moriarty is very rarely found outside of Co Kerry and if you meet a Riordan you can be fairly sure he or she will speak with the distinctive accent of Co Cork. Both names are still common in their home areas but uncommon elsewhere.

Even with very frequently occurring names such as Brennan, which is pretty much ubiquitous, concentrations in small areas still occur.

There is a large concentration of Brennans in Donegal, among them the well known Irish singer Enya (left), whose real name is Eithne Ní Bhraonain.

The Castlecomer Brennans

There are so many families with the surname Brennan around the town of Castlecomer in Co Kilkenny that nicknames are used to distinguish them, so that you have Brennan Con,Brennan Duff or Brennan Joes. These are sometimes even included when addressing mail.

The story of the Brennans of Castlecomer shows how families can persist in an area against all the odds. That the Brennans have survived  at all, let alone thrived, is remarkable.

Prior to the 12th century they were the dominant clan in what is now the Kilkenny City area, effective rulers of vast areas of excellent land. When the Normans arrived they assumed ownership almost all lands around the city and the Brennans were driven out to less fertile lands around Castlecomer.

In the 17th century they lost ownership of that land to the Wandesfordes, an English family who were granted the lands around Castlecomer by the Crown and relegated the Brennans to the status of tenent farmers, paying rent on lands they had previously owned.

But through all the tribulations down the centuries they survived and remain very numerous in their home territory, where they now once again own the land they farm. Quite a story of dogged determination.

Scots Gaelic Names

It is often erroneously said the Mc indicates Irish origin and Mac Scottish origin. In fact there is no difference at all. The languages of both countries are similar and the two are effectively interchangeable and say nothing whatever about origin.

It can sometime be tricky to decide whether a name begining with Mac or Mc is of Irish or Scots Gaelic origin, but there is a good hint in the religion of its bearer and where in Ireland they live now or came from.

Scottish names are by far more common in the Northern counties, where waves of Scottish planters settled in times past, than in any other part of Ireland. Those with names of Irish origin are predominantly Catholic, those whose names originated in Scotland mainly protestant.

So a Protestant McSweeney from Donegal almost certainly has Scottish ancestry, while a Catholic McSweeney from Cork has an Irish name and is from an unrelated family.

Published: November 16, 2008 | Updated: March 31, 2017 | Image Credits

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  • Charlene says:

    Is the surname Gore Irish?

  • Virginia says:

    Would like to know origin and Gaelic version of last name Lucid. Seems my Grandparent came from Kerry and Kilkenney.

    Thank you

  • Carmen Feakes says:

    The names McManus ,Walls,Reilly are they of Irishe origin?

  • David Cooper says:

    I am clutching at straws and just wondered if maybe you could help..
    would you know what the Cooper name would have been coming out of France as Huguenots and settling in Dublin as Cabinet makers my great gt gt gt grand father was known as John Cooper born, b)1800 in Dublin and was himself a cabinet maker so I am to believe that we are Huguenots and haven’t a clue in finding the correct name of my forefathers I would love to prove that I am a Huguenot and indeed love to find out exactly when and where we had left France and where my family had come from before Dublin . are you able..?

    • Liz H says:

      Hi David,

      I’ve only just seen your question, but if you find my reply, the French for a cooper is a tonnelier.
      Bonne chance!

  • B. Mac Gabhann says:

    I was just enquiring as to what the difference is between Smith and Smyth? Is there a religous difference or does it mean anything at all. As far back as I can go my ancestors were Irish Catholic, spelling our name Smith, but my grandfather seemed to change to Smyth. I wonder if there is a significant reason for this or did he just prefer one spelling to another?
    Any advice would be much appreciated.

    • Julie says:

      My Protestant Irish great grandfather came from County Carlow in the south even tho he declared he was from the north. His surname was Smyth but when he arrived in Australia he changed it to Smith. I don’t think religion played a part in it, I read on a map outlining clans if your surname is Smith/Smyth it would of been ‘McGowan’ and they come from the north further to the middle of Ireland.

  • Bob says:

    Indeed Pardraig the same can be said for McSheehys and McDonnells as Galloglaigh they fought for northern and southern chieftains and many settled in the areas they were contracted to, exception were the McCabes Galloglas who settled in Oriel mainly Co Monaghan where their name is numerous today they fought with McMahons! O Reillys Maguires and some and O Ruaics

  • Even though all the names in my family are gaelic my Great Grandmother from County Longford was named Whitney. Can anyone tell me where that name originated from? Thankyou. Patricia Farrell.

    • Danny says:

      Whitney de Fuitnigh. This name is not numerous, but has been found in east Leinster since the fourteenth century. It is derived from an English place-name

  • martin powers says:

    Thank You!   I find all of this very interesting…My name Powers, as far as I know in Norman in origin… County Waterford, Ireland is a strong hold for the name Power without S…I think any name in Ireland that had a Anglo ring to it, the Irish would make suttle changes to it like Brown, to Browne,Green, to Greene,and so on…George Carlin, the comedian once said “the Irish would put the final E on anglo names just to piss them off”…In closing there is a botanical gardens out side Dublin called ” Powers’ Court” and a good Irish wiskey John Powers, or Power…again thank You!!
    Martin C Powers

    • Calvin Mulligan says:

      We visited Powerscourt in 2016 and toured the gardens. They are a masterpiece, supposedly rated by National Geographic as third most beautiful in the world. The ranking aside, we hope to go back again.

  • Dave Skelly says:

    How come your list of surnames doesnt go past O in the alphabet? I’m trying to find information on the surname Skelly. so far i have only found the crest of arms but not its origin other than its irish. any help would be greatly appreciated

    • Danny says:

      Mac Scalaidhe Mac Scally. Traditionally and by present location this name belongs to Counties Rosommon and Westmeath. Sometimes it is found with the prefix Ó in Irish. Skelly is a form of Scally found in Oriel (Airghíalla in Irish). Airgíalla at its peak spanned the modern Irish counties of Derry, Monaghan, Tyrone, along with parts of Armagh, Fermanagh and Louth. The later constricted kingdom of Airgíalla survived in Monaghan—which was known as Oirghialla and Oriel after the Norman Invasion of Ireland—until the end of the Gaelic order in Ireland.

  • padraig says:

    good article with one little mistake. Regarding the MacSweeney clan of Donegal and Cork, they are both descendents of Hebridean gallowglasses. Also in Donegal, indeed most of the north, they have dropped the Mac and are a staunchly Catholic clan. Very few of them converted to Protestantism. They are a pre- plantation clan

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