10 Irish American Surnames Explained

Family History
12 March 2021
by Rebecca Dalzell

Over four million Irish immigrants came to the United States between 1820 and 1930. Their surnames are still common around the country, especially in historic enclaves in the Northeast.

Many originally had a tell-tale “O” before the name, which meant “descendant of” in the gaelic Irish language, but it has largely been dropped. With or without the O, according to a tally of surnames in the 2010 U.S. Census*, these are 10 of the most common Irish surnames in America.

And you can explore the roots of your own Irish surname with the free surname widget on Ancestry.

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1. Murphy

#64 (308,417 people)

At the end of the 19th century, Murphy was the most prevalent surname in Ireland and was particularly associated with Counties Cork and Wexford. So it’s not surprising that it’s now the most common Irish surname in the United States.

A sketch of Nathan Oakes Murphy Governor of Arizona Territory and Territorial Delegate to the U.S. House of Representatives
Nathan Oakes Murphy (1849–1908), Governor of Arizona Territory and Territorial Delegate to the U.S. House of Representatives.


It derives from “murchadha,” meaning “sea-warrior,” a personal name once popular in Tyrone, Northern Ireland.

2. Kelly

#74 (267,394)

Kelly is the English version of the Gaelic Ó Ceallaigh, or “descendant of Ceallach,” an ancient personal name meaning “bright-headed” or “warlike.” It has origins in several different parts of the country, which accounts for its popularity today. A prominent branch descends from a chief of Ui Maine, a kingdom in western Ireland, who was the first recorded Ceallach, in 874.


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3. Sullivan

#105 (220,990)

Sullivans have been around since before the Anglo-Norman invasions, which forced them west from Tipperary to Munster. The name is an Anglicized version of Ó Súilleabháin, a personal name that likely meant “dark eye” in Gaelic.

4. Butler

#108 (218,847)

Rooted in a Norman word meaning “wine steward,” Butler came to denote the top servant of a household. The name arrived in Ireland in the 12th century, when Theobald Fitzwalter was appointed Chief Butler of Ireland under Henry II.

A portrait of Thomas Butler, 10th Earl of Ormond, wearing armor
Thomas Butler, 10th Earl of Ormond (1531-1614) in three-quarter armor holding a wheelock pistol

His son took the name le Botiler and his children went by Butler, building strongholds in Tipperary and Kilkenny.

5. Kennedy

#146 (176,865)

Though associated in the United States with the 35th president, Kennedy actually derives from a Gaelic name, Ó Ceannéidigh or Ó Cinnéide, meaning “ugly head.” It’s both a Scottish and Irish name, but most Kennedys who came to America were from Ireland. The medieval O’Kennedys had a barony in Upper Ormond, Tipperary, where the name is still prevalent. JFK’s family, however, came from County Wexford.

6. Ryan

#193 (143,452)

Ryan is a translation of the Gaelic Riagháin, Riain, or a shortened version of Maoilriain. These names are so ancient their exact meanings are unclear, but they were possibly tied to water or kinship. Ryan can also stem from Ruaidhín, meaning “little red one.”

A headshot of Walter D'Arcy Ryan, GE director of Illuminating Engineering Laboratory
Walter D’Arcy Ryan (1870-1934), GE director of Illuminating Engineering Laboratory, responsible for lighting of the Panama-Pacific International Exposition in San Francisco

O’Riains were chiefs in Counties Carlow and Wexford, while O’Maoilriains had pastures in Tipperary and Limerick. The name Ryan still predominates in the southern half of Ireland.

7. Carroll

#215 (134,317)

Deriving from the Gaelic word for “hacking,” Carroll is the Anglicized version of Cearbhaill, a personal name meaning “fierce in battle.” The most famous ancestor was Cearbhaill, King of Ely, an 11th-century warrior in what is now Counties Tipperary and Offaly. Carrolls from that region came to the US in the late 17th century, when they settled in Maryland.

8. O’Brien

#258 (118,557)

Brian Boru was high king of Ireland from 1002 to 1014. He unified Munster and wrestled control over the southern half of the island, gaining enormous fame. His descendants, the O’Briens, became one of the country’s chief dynasties. The Gaelic name Briain was likely related to “hill” at first, then came to denote an eminent person and also survives as the surname Bryan.

9. McCoy

#278 (110,744)

Multiple Irish surnames stem from the Gaelic Mac Aodha, or “son of Aodh,” the pagan god of fire. Regional accents and English translations have turned it into McCoy, McGee, McKay, and McKee. McCoy tends to be the spelling in Northern Ireland, where it’s a common surname in Counties Monaghan and Armagh, though it’s also found farther south in County Limerick.

10. Walsh

#295 (105,079)

Though it’s one of the most common surnames in Ireland, Walsh was originally a name for outsiders. It’s a loose English translation of the Gaelic word “Breathnach,” meaning “Briton” or “Welshman”—a foreigner. Variants include Welsh and Welch.

 A snapshot of Edward Walsh, record-holding pitcher, in a baseball uniform
Edward “Big Ed” Walsh (1881 – 1959), record-holding pitcher inducted into the Baseball Hall of Fame in 1946

It was particularly used to describe those who came over with Strongbow’s Anglo-Norman invasion in 1170. The vast majority of Walshes on immigration passenger lists came to the United States from Ireland.

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*Based on “Frequently Occurring Surnames from the 2010 Census” from the United States Census Bureau.


Carroll, Louise. “Carroll, O’Carroll, MacCarroll, MacCarvill, MacCearbhaill.” Irish America – Irish America Magazine, 2003. https://irishamerica.com/2003/08/carroll-ocarroll-maccarroll-maccarvill-maccearbhaill/.

“Charles Carroll the Settler.” Charles Carroll House, August 12, 2015. https://charlescarrollhouse.org/the-carrolls/the-settler.

“Discover the Meaning and History behind Your Last Name.” Last Name Meanings and Origins | Search Surnames at Ancestry.com®. Accessed February 18, 2021. https://www.ancestry.com/learn/facts.

Grenham, John. “The Little Book of Irish Clans : Grenham, John : Free Download, Borrow, and Streaming.” Internet Archive. Secaucus, N.J. : Chartwell Books, January 1, 1994. https://archive.org/details/littlebookofiris0000gren/page/14/mode/2up.

O’Laughlin, Michael C. The Book of Irish Families, Great & Small. United States: Irish Genealogical Foundation, 2002.