The Origins of Your Irish Surnames.

Would you like to know a little more about the typical origins of your Irish Surnames? Then read on...

Now Reading:

The Origins of Your Irish Surnames.

Let’s  take a deeper look at the – Irish surnames in your family. Where did your Irish surnames come from? How did they evolve? You have probably already discovered that the surnames in your family are the best way to track and audit the journey of your family and kin.

A problem quickly arises when you start your investigation and notice all the disconnections come to the surface. As you continue your research, ancestry websites and internet user groups can be a fabulous way of discovering some of those fragments. However, they can also be full of frustrating “red herrings” and distractions.

I have found that most of us need a roadmap. With this roadmap, you can better understand the areas where the genealogical gold is likely to be buried. With this map, you can quickly decide what sounds likely – and what is evidently nonsense.

This article aims to be that roadmap.

The Obstacles in Your Way.

One thing a roadmap does very well is to outline and locate the obstacles in your way. Many of us have come across the following obstacles already when digging deeper into our Irish Heritage:

  1. Missing Irish Records (burned apparently in 1922).
  2. The many spelling variations of Irish surnames.
  3. Clerical error (often absurd) when a name was spoken, but transcribed to something the clerk was more familiar with (like an English equivalent name).
  4. Finally, in keeping with their sense of escape and starting a new life – many of our ancestors assumed new surnames that they felt better suited their new life station (losing the “O” just being one example).

Blog 1

Edward Neafsey  (author of the very useful Surnames of Ireland) highlights this very well. When he describes the migration of his own surname. His surname comes from the original Irish O Cnáimhsighe (get your tongue around that one!). While his grandfather’s sister was spelled “Navisey” on her baptismal book, his grandfather was entered as “Neafsey” in the same book. It was spelled as “Kneafsey” on his birth cert. And when he moved to England his marriage cert spelled his name “Neafey”. One family, five variations.

Some surnames like Murphy and Kelly may not have changed so much. However other Irish names have mutated in a similar way over the generations.

Article18 So, for the rest of this article we will take the longer view. We will stretch back over the generations to a time when surnames first came into use in Ireland. We will look at some of the outside influences, events and naming conventions that have changed your Irish names. Evolving them from what they were originally to what they are now.

Let’s Start at The Beginning.

My own postal address is:

Mike Collins,


County Cork, Ireland.

This is a typical Irish postal address that you find today outside the cities of Ireland. As you can see, it relies on the local knowledge of the postman to figure out which specific house I live in. The one absolute he has to deal with is my name – Mike Collins.

You may notice the absence of Post and ZIP codes. Why am I showing you this?

Well, it illustrates an attitude that has persisted over many thousands of years in Ireland. Originally we were a nomadic and pastoral nation. We had land – but we followed our animals depending on season and climate.

blog6 From the 900s onwards the population increased in Ireland as elsewhere in Europe. As political stability increased across Europe along with a better climate for growing food and fewer raids by marauders – so too did the hierarchal structure we know as feudalism. Land became parcelled, was owned by freeman, worked by serfs – and overseen by the lords. This situation allowed for the later start of Postal and ZIP codes in a way.

In Ireland things were different.

While our population also increased, so too did the power and influence of a more centralised church – as well as the power of a group of overlords and kings assuming control of entire provinces in a real sense for the first time.

Top 250 Irish Surnames

Just some of the names among our Letter from Ireland subscribers.

The Evolution of Irish Surnames.

I believe that the very real problem of administering a moving and population, enforcing the Brehon laws and simply keeping tabs on the increasingly complex genealogies and rights of inheritance – caused Ireland to be possibly the first country in Europe to introduce the “surname”.

(This article evolved in conversation with our free Letter from Ireland subscribersif you would like to add your Irish surnames to our list, then just signup for your free weekly Letter from Ireland by clicking here.)

We had to lock the name in – as the locations were too mobile. This surname would become the one constant in a moving sea of variables and possibilities (like in my postal address above).

The first recorded surname in Ireland is O’Clery (Ó Cléirigh) in what is now modern County Galway around  920 AD. Although the creation of surnames in Ireland may have began early, it slowly continued for over six hundred years.

By the end of the eleventh century the main families of Ireland (those whom had their genealogies recorded) had acquired many of the surnames we know today. They were constructed using either an “Ó” (short for Ua – “descendent of”) or a “Mac” (“son of”) followed by a personal name of an illustrious ancestor.  The surnames of Ireland’s ruling families can typically be tracked down to one single individual. The O’Neills of the Northern Uí Neill in Ulster take their surname from one of their kings –  Niall Mac Aoidh. He died in 917.

Settling down for the evening outside O'Neills

Settling down for the evening outside O’Neills

However, the process continued for some hundreds of years as different major families (such as the O’Neills) went on to split into further groups and assume new surnames for that splinter group.

Always Start with the Irish for Your Name.

If you are looking for a “true north” to go with your surname “map” – then this is it. Given all the spelling variations that you are likely to come across, there is ONLY one correct spelling.

Yes. Only one.

I have found that the ONLY way to pin down that name is to learn the original Irish language version of that surname.

Have a think about it.

McCarthys Bar, CastletownbereTake the surname O’Reilly – which is also heard as Riley, Reilly, O’Riley (and other versions I’m sure I’ll hear one day).

The thing is – none of these are correct!

These are versions that have sprung up over centuries with the introduction of English in Ireland, emigration, mutation and so on.

The most useful starting point is the original Irish language version: Ó Raghailligh (pronounced Oh Rah-al-ig – just say it fast). This is the root for all the O’Reilly English language versions out there.

But of course,  the Reillys have it easy (and the McCarthys, O’Briens, Murphys and so on) as they were never pegged to an equivalent English name. When English speakers heard O Raghailligh spoken for the first time – they just said it as they heard it: O Reilly/Riley

The “trouble” started when an English speaker heard another name for the first time – AND it reminded them of an English name that they already knew – and that’s the name they gave!


O’Mahony of Cork.

The Surname Hammill.

To illustrate, let’s take an example of a lesser-known Irish name – Hamill. If you think this sounds like an English name – you are right! But if you come across the name in your Irish family tree, it most likely has a different source to the Hamills you will come across in England (it is facts like this that cause your frustration with mega-ancestry sites – their focus is on the greater population of the surname – not on us – the little Irish contingent!).

Back to Hamill. Hamill comes from the original Irish “Ó hAdhmaill” (pronounced Oh–ham-will). This surname comes from a nickname-derived first name “Adhmall”. This Gaelic family were part of the Cenél Eoghain part of the Northern Ui Neill in what is now County Tyrone.

In the case of Ó hAdhmaill, an English speaker/clerk heard the Irish name spoken – it reminded them of the English name Hamill – a name they were already familiar with – and so “Hamill” became a given name for this old Gaelic family. This process happened slowly from the 1600s onwards as the English administration spread through the island of Ireland.

You’ll notice on many ancestry sites that surnames like ‘Hamill’ are included. However there is still a small portion of Irish folks jumping up and down in the corner protesting that this is also an Irish name! And they are right – to a point!

The Surname Ryan

Ryans of Tipperary

Maguire or McGuire?

So, when a reader chastises me for using the incorrect spelling for an Irish surname (e.g. Maguire instead of McGuire) – I reply that the ONLY correct spelling is the original Irish. So, I recommend that you find out the original Irish for your Irish surname. Then learn to phonetically pronounce it. Then learn all the English variations that have come along for this name over the centuries. This will open up a whole new world of understanding in your Irish Heritage journey. As you “widen the net” to include many possibilities of mutations of your surnames. But all anchored to a single Irish language origin.

Right, we are almost there. But let’s finish off the roadmap to guide our journey with three questions that I often get from the readers of Your Irish Heritage.

3 Reader Questions to Finish Off Our Roadmap.

To finish off our roadmap, let’s look at three questions I often get asked. With these answers we will finish off the map that we are developing – a map to help you anticipate and avoid the main obstacles when reaching your Irish surname family tree.

Question 1.

Recently I got an email from a lady who goes by the surname of “McGee”. She asked: “I met a lady called “McCoy” last year – she insisted we are distant cousins – how could that be?”

Looking through our reader list on Your Irish Heritage – I notice that we have Keyes, MacHugh, Gee, McGee, O’Hea, Hayes, MacKaw, Makay and McCoy. All of these Gaelic surnames have something in common. They have all been anglicized from the same Irish surname – Aodh. “Mac Aodha” (son of Aodh) or “O hAodha” (descendant of Aodh).

(Would you like to add your Gaelic surname to our list? Simply signup for your free weekly Letter from Ireland by clicking here – and we’ll let you know how to join in the fun.

Aodh/Aedh (pronounced “Aay” – rhymes with “hay”) was a very popular first name in Ireland up to the 10th century.

Clonakilty Black Pudding Up to that point individuals were known by their first names and lineage. So, individuals were known as “Aodh son of Donnchadh” and so on.

And then from the 900s to 1100s – families adopted the surname system we know today. Lots of families across Ireland (and Scotland) chose the name MacAodha or O hAodha. And that got anglicized into the different surnames we see above over the next few centuries.

So I got back to Mrs. McGee and told here while we all may be cousins going back to Adam and Eve – you would have to go back almost as far to make this Mrs. McCoy your cousin.

Question 2.

“Why do YOU write MacCarthy as McCarthy?” (Read that one again – there is a difference). Questions like this I’m asked on a regular basis.

Connolly, Skibbereen As we said earlier, Ireland was probably the first country in Europe to introduce a surname system in the 10th century.

The Gaelic surnames of the time were formed around an illustrious ancestor. For example the O’Briens from Brian Boru.  These Irish Gaelic surnames typically have one of five prefixes:

  1. “O” as in O’Brien or O’Neill.
  2. Mc or Mac – as in McCarthy or McCoy.
  3. Gil – which comes from the Irish “Giolla” meaning follower – as in Gilmartin.
  4. Mul – like in Mulrooney or Mullarkey.
  5. Sometimes a combination of the above as in Mac Giolla Íosa (MacAleese).

A smaller class of Irish surname named the family after an occupation or profession. For example; McInerney ( Mac an Airchinnigh in Irish) which means “son of the eranagh” (a type of lay abbot). Another example is; Hickey (in Irish O hIcidhe) which comes from the Irish for Physician or Healer.

The  difference between a Mc and a Mac (and some people wonder is the “Mc” Irish and the “Mac” Scottish? The answer is: there is no difference! Mc is simply an abbreviation of Mac.

McCarthy Also, you are very unlikely to hear a surname starting with “O” in Scotland (although a very few do exist).

Question 3.

A Mrs. Sullivan contacted me and commented “it’s a pity our family lost the “O” when we came to the States – I wonder can we get it back?”

But, there’s a bit more to it than that. Gaelic and Catholic people were discriminated against by the English ascendency – from the 1600s onwards. This led, gradually, to the abandonment of the Os and Macs in many surnames. O’Murphy became Murphy, O’Kelly became Kelly and so on.

However, in the late 19th century there was a Gaelic cultural resurgence in Ireland and many of these surnames took their Os and Macs back as a badge of Gaelic pride.

Take “O’Sullivan” as an example – when we look at the census data for Ireland, the following comes up:

Year:               Percentage using the prefix O 1866               4% 1890               12% 1914               22% 1944               62%

So, you can see that many emigrants who left Ireland during famine times (BEFORE 1866) were missing their Os and Macs – and mostly never took them back. Whereas a high percentage of those who stayed in Ireland had them reinstated.

Maybe it’s time to take your O or Mac back?

In Conclusion.

I realise that we have covered a lot of ground in this chapter. As well as that, we went WAY outside our remit of “around the time of 1152AD”.  Hopefully you’ve found this letter useful in understanding the evolution of your Irish surname.

I also hope that this chapter gives you a useful outline map to move quicker towards the genealogical gold that you are seeking!

Slán for now,


Plus Member Comments

Only Plus Members can comment - Join Now

If you already have an account sign in here.