An Irish surname is a little piece of history. Many date as far back as the 10th and 11th centuries, and the meanings behind them give us a fascinating glimpse of medieval Ireland.
Irish people started using surnames much earlier than many other countries. In fact, you could say we were trailblazers of the trend. They took off here around the early 900s but were introduced much later in Britain and mainland Europe. An Irish surname was derived from the father’s name, using the prefix Mac (son of) or Ó (grandson of) for males and Ní or Nic (daughter of) for females.
Why were surnames adopted so early in Irish society? Possibly because family background is so important in Ireland. If someone knew who your people were, they would instantly know a lot about you. Even today, Irish people have a curious need to know this sort of thing, it’s second nature to us… “Who’s yer man? Would he be related to the O’Neill’s down the road. Ah, I see.” It tells us a lot.
Our system of Brehon Laws might provide another explanation for the early use of surnames. Under this progressive system, fines were issued as punishment for committing a crime. And since the wrong-doer’s family were responsible for paying the fine, it would be useful to know which family he or she hailed from.
You would think that surnames being hereditary would be an advantage to anyone researching their family history. Unfortunately however, as with many things in Ireland, it’s not that simple. According to genealogist John Grenham, it’s impossible to exaggerate just how unreliable records were before the 1900s. Often names were written down incorrectly by non-Gaelic speakers and since nearly everyone was illiterate, many didn’t realise their names weren’t recorded properly.
Where In The Country?
Nevertheless, the hereditary nature of each Irish surname means that names traditionally belonged to certain areas. This map from the dedicated genealogy website of the National Archives of Ireland shows where in the country your original namesake came from.
There are many interesting peculiarities about Irish surnames and it’s worth looking into the history of your own name. For instance, research shows that 17% of Y (male) chromosomes in the north-west of the island share a genetic link with a 5th century warlord called Niall of the Nine Hostages. He was part of the Uí Néill dynasty, from which 25 Irish surnames ultimately descended.
Another name with an interesting history is O’Brien. This comes from the Irish O Briain (grandson of Brian) and is associated with the legendary Brian Ború, who fought the Vikings at the Battle of Clontarf in 1014. The O’Brien’s original ancestors are thought to date from the 6th Century. They were known by the name of the kingdom in Munster which became the seat of their power in the 900s – Dál Cais. After the death of Brian Ború, his descendants adopted the O Briain name.
Some very common surnames, like O’Sullivan and Ryan, have a single major ancestor. This is not the case in neighbouring Britain, where research indicates that the more common the surname, the greater the number of founders. This demonstrates how close-knit Irish society was. And still is today – about half of the people with these names share a genetic link with their original namesake.
However, some of the most common surnames, like Murphy and Kelly, have numerous founders. This probably explains their high frequency today, since they’re the top two registered surnames for babies in 2018.
Most Popular Irish Surnames
The top 10 surnames for new babies in 2018 (in descending order) were Murphy, Kelly, Ryan, O’Brien, Byrne, O’Connor, Walsh, O’Sullivan, McCarthy & O’Neill. If you belong to one of these clans, you’re in good company.
In fact, there’s been very little change in the top 10 surnames over the last hundred years. In 1909, Robert Matheson wrote a report on Irish surnames, based on the Birth Index of 1890. We’ve given you the top 50 below, along with their meanings – some of which are hilarious. If yours hasn’t made the cut, search for it here.