Usually the honest answer is not yes or no. A name can be Gaelic; it can be Norman and Irish for eight hundred years; it can have come with the plantations and belong to families who have been here four centuries since; and it can be two unrelated families who ended up spelling their names the same way. Those are four different answers, and most pages that promise you one are picking whichever flatters.
A name formed in Irish, from an Irish ancestor, before English was spoken here. These are the Ó and Mac names, and the answer to “is it Irish” is simply yes.
Norman families who came after 1169 and became, in the old phrase, more Irish than the Irish themselves. Eight and a half centuries in the country is long enough: these names are Irish, they are just not Gaelic. Many took an Irish form — Walsh is Breathnach, Burke is de Búrca.
Scandinavian settlers who arrived from the 9th century, founded the port towns and married into Gaelic Ireland. Their names came through Irish and are Irish names by any measure that matters.
Names that came from Scotland, England or Wales, most of them during the plantations of the 1600s. A family carrying one may have been in Ireland for four hundred years, which is longer than most nations have existed. Whether you call that Irish is not a question a surname can settle.
The hardest case, and the most common one behind the question. A Gaelic sept and an incoming family ended up with the same English spelling, and the two are unrelated. Your name cannot tell you which you are. The records can.
Yes, though not a Gaelic one. Fleming means “man from Flanders”; Flemish settlers came with the Normans after 1169 and the name is Pléimeann in Irish. It has been an Irish surname for roughly eight hundred years.
Stewart is Scottish in origin (it means the steward of the royal household) and came to Ulster in numbers during the plantation of the 1600s. Many Irish families have carried it for four centuries since. It has no Irish-language form because it never had one.
Not in origin: Wilson means “son of Will” and arrived from Scotland and England, largely with the plantations. It is one of the commonest surnames in Ulster today, borne by families who have been in Ireland for centuries.
It often is. In Ireland Smith is frequently a translation of Mac Gabhann, “son of the smith”, a Gaelic sept of Breifne who rendered their name into English rather than spelling out the sound. An Irish Smith and an English Smith can be spelled the same and be unrelated.
The name alone often cannot tell you, because the same spelling can cover a Gaelic sept and an incoming family. What settles it is the record: where the name was densest in the 1901 and 1911 censuses and in Griffith's Valuation, and what the parish registers say. Start from the county, not from the name.
Almost always for Ó, which is a specifically Irish formation. Mac is shared with Scottish Gaelic, so a Mac name may be Irish or Scottish — and after the gallowglass and the plantations, plenty of Scottish Mac names are long settled in Ireland.
By any practical measure, yes. Burke, Fitzgerald, Power, Barry and Walsh arrived after 1169 and are among the commonest surnames in Ireland. Most took Irish forms (de Búrca, de Paor) and the old phrase for these families was that they became more Irish than the Irish themselves.
Is your name here and the answer wrong for your family? That happens, and we would like to know — tell us. · All surnames A–Z · Surnames in Irish · Irish form → English name · Gaelic surnames · Norman surnames