Explore the Family Name O'Reilly

The meaning of O'Reilly

Irish (Cavan, Meath): Anglicized form of Gaelic Ó Raghailligh ‘descendant of Raghailleach’, Old Irish Roghallach, a personal name of unexplained etymology. This is the name of a chieftain family in County Cavan, related to the O’Rourkes. In Anglicized form it has also been confused with Ó Raithile found in Munster, usually Anglicized as O’Rahilly. Some characteristic forenames: Irish Brendan, Mairead, Aidan, Colm, Declan, Dermot, Dympna, Eamon, Finbar, Brennan, Brian Patrick, Brid.

Dictionary of American Family Names, 2nd edition, © Oxford University Press, 2022.

How common is the last name O'Reilly in the United States?

Based on the Decennial U.S. Census, the surname O'Reilly held steady in popularity between 2000 and 2010, maintaining a rank of 2946 and a count of 11,224 individuals. The proportion of individuals with the O'Reilly surname per 100,000 people also remained consistent at 4.16 during this decade. There was no change observed in any of these categories over this ten-year period.

20002010Change
Rank#2,946#2,9460%
Count11,22411,2240%
Proportion per 100k4.164.160%

Race and Ethnicity of people with the last name O'Reilly

In terms of ethnicity based on the Decennial U.S. Census data, the majority of individuals with the O'Reilly surname identified as White, with this category making up 93.40% of those surveyed in both 2000 and 2010. The next most common ethnic identities were Hispanic at 2.63%, Black at 1.74%, and those identifying with two or more races at 1.59%. The Asian/Pacific Islander and American Indian and Alaskan Native categories each made up less than one percent of the total, at 0.46% and 0.19% respectively. No changes in these percentages were observed from 2000 to 2010.

20002010Change
White93.4%93.4%0%
Hispanic2.63%2.63%0%
Black1.74%1.74%0%
Two or More Races1.59%1.59%0%
Asian/Pacific Islander0.46%0.46%0%
American Indian and Alaskan Native0.19%0.19%0%

O'Reilly ancestry composition

23andMe computes an ancestry breakdown for each customer. People may have ancestry from just one population or they may have ancestry from several populations. The most commonly-observed ancestry found in people with the surname O'Reilly is British & Irish, which comprises 67.5% of all ancestry found in people with the surname. The next two most common ancestries are French & German (12.0%) and Italian (5.7%). Additional ancestries include Eastern European, Spanish & Portuguese, Scandinavian, Indigenous American, and Ashkenazi Jewish.

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ANCESTRY BREAKDOWNCOMPOSITION
British & Irish67.5%
French & German12.0%
Italian5.7%
Other14.8%
O'Reilly

Possible origins of the surname O'Reilly

Your DNA provides clues about where your recent ancestors may have lived. Having many distant relatives in the same location suggests that you may all share common ancestry there. Locations with many distant relatives can also be places where people have migrated recently, such as large cities. If a large number of individuals who share your surname have distant relatives in a specific area, it could indicate a connection between your surname and that location, stemming from either recent ancestral ties or migration.

Based on 23andMe data, people with last name O'Reilly have recent ancestry locations in the United Kingdom of Great Britain and Northern Ireland and Ireland.

RECENT ANCESTRY LocationPercentage
Greater London, United Kingdom88.00%
Glasgow City, United Kingdom88.00%
Greater Manchester, United Kingdom88.00%
Tyne And Wear, United Kingdom87.50%
Lancashire, United Kingdom87.10%

What O'Reilly haplogroups can tell you

Haplogroups are genetic population groups that share a common ancestor on either your paternal or maternal line. These paternal and maternal haplogroups shed light on your genetic ancestry and help tell the story of your family.

The top paternal haplogroup of people with the surname O'Reilly is R-A260, which is predominantly found among people with European ancestry. Haplogroup R-A260 is descended from haplogroup R-M343. Other common haplogroups include R-M222 and R-CTS241, which are predominantly found among people with European and European ancestry. Other surnames with similar common haplogroups are: Reilly, Geraghty, Fallon, O'Reilly, Mcdonough, Masterson, Mcgovern, Kiernan, Garrity, Tighe.

The most common maternal haplogroups of people with O'Reilly surname are: H1, H3, H. These most commonly trace back to individuals of European ancestry.

o-reillyPaternal Haplogroup Origins R-M343
Paternal Haplo Image

Your paternal lineage may be linked to Niall of the Nine Hostages

The spread of haplogroup R-M222 in northern Ireland and Scotland was likely aided by men like Niall of the Nine Hostages. Perhaps more myth than man, Niall is said to have been a King of Tara in northwestern Ireland in the late 4th century C.E. His name comes from a tale of nine hostages that he held from the regions he ruled over. Though the legendary stories of his life may have been invented hundreds of years after he died, genetic evidence suggests that the Uí Néill dynasty, whose name means "descendants of Niall," did in fact trace back to just one man who likely bore haplogroup R-M222, a branch of R-M269.The Uí Néill ruled to various degrees as kings of Ireland from the 7th to the 11th century C.E. In the highly patriarchal society of medieval Ireland, their status allowed them to have outsized numbers of children and spread their paternal lineage each generation. In fact, researchers have estimated that between 2 and 3 million men with roots in north-west Ireland are paternal-line descendants of Niall.

Your maternal lineage may be linked to Marie Antoinette

Because it is so dominant in the general European population, haplogroup H also appears quite frequently in the continent's royal houses. Marie Antoinette, an Austrian Hapsburg who married into the French royal family, inherited the haplogroup from her maternal ancestors. So did Prince Philip, Duke of Edinburgh, whose recorded genealogy traces his female line to Bavaria. Scientists also discovered that famed 16th century astronomer Nicolaus Copernicus traced his maternal lineages to haplogroup H.

Maternal Haplo Image

What do people with the surname O'Reilly have in common?

Spoiler alert: it's complicated. People with the same last name are usually no more genetically similar than a randomly sampled group of people from the same population. That said, people with the same surname are more likely to have similar ancestries than randomly sampled individuals. The reason is the tendency of people with similar cultural or geographical backgrounds to preferentially mate with one another. That's why people who share a surname may be more likely to share traits and tendencies in common than people within the general population. Check out the percentages below to see the prevalences of tastes, habits, and traits of people with your surname compared with prevalences among 23andMe users.

Preferences

O'Reilly

Chocolate Ice Cream

Prefers chocolate flavored ice cream over other flavors.

"O'Reilly" Surname 43.1%

23andMe Users 41.3%

Traits

O'Reilly

Misophonia

When sounds made by others, like the sound of chewing or yawning, provoke strong emotional reactions in an individual.

"O'Reilly" Surname 29.3%

23andMe Users 27.9%

Habits

O'Reilly

Sugary Drink

Drinks one or more sugary drinks per day.

"O'Reilly" Surname 18.3%

23andMe Users 21.1%

Wellness

O'Reilly

Migraine

A severe headache characterized by intense pain, sensitivity to light and sound, and often accompanied by nausea and vomiting.

"O'Reilly" Surname 18.3%

23andMe Users 16.4%

Are health conditions linked to the last name O'Reilly?

The short answer is that, if there is an association between surname and health, it's usually more about your ancestry than your name. Individuals with a given surname are no more genetically similar than the general population but often have similar ancestries. The populations of people associated with those shared ancestries often have sets of genetic variations, also known as alleles, in common. Some of those alleles are associated with a greater likelihood of developing certain diseases.

Disease variant frequency by ancestry

Disease allele frequencies in populations associated with the surname O'Reilly are shown below. Important Note: not everyone with a disease allele will develop these health condition

Age-Related Macular Degeneration

Y402H variant

Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss among older adults. The disease results in damage to the central part of the retina (the macula), impairing vision needed for reading, driving, or even recognizing faces. The 23andMe Health + Ancestry DNA test includes the two most common variants associated with an increased risk of developing the condition: the Y402H variant in the CFH gene and the A69S variant in the ARMS2 gene. Learn more about Age-Related Macular Degeneration

British & Irish 62.1%

23andMe Users 57.2%