Find out how popular the last name Brennan is in the United States and learn more about the meaning, history, and race and ethnic origin of people in America who are named Brennan.

Brennan, like all of the last names we have data for, is identified by the U.S. Census Bureau as a surname which has more than 100 occurrences in the United States in the Decennial Census survey. The most recent statistics we have for the Brennan surname is from the 2010 census data.

Popularity of Brennan in America

Brennan is the 701st most popular name in America based on the data we have collected from the U.S. Census Bureau.

The Brennan surname appeared 49,238 times in the 2010 census and if you were to sample 100,000 people in the United States, approximately 17 people would have the surname Brennan.

We can also compare 2010 data for Brennan to data from the previous census in 2000. The table below contains all of the statistics for both years in a side-by-side comparison.

The history of the last name Brennan

The surname Brennan originated in Ireland, derived from the Gaelic name O Brannagain, which means "descendant of Brannagan". Brannagan was an ancient Irish personal name that meant "raven" or "blackbird". The name was first found in County Kilkenny and later spread to other parts of Ireland.

The earliest recorded instances of the surname date back to the 13th century. In medieval Irish records, it was often spelled variations such as O'Brenaghan, O'Brennan, and O'Branagan. The Brennan name is believed to have been present in Ireland since before the arrival of the Normans in the 12th century.

One of the earliest recorded Brennans was Dermot O'Brennan, a chief of the Uí Duach sept in County Kilkenny, who lived in the late 12th century. In the 14th century, the Annals of the Four Masters mention a notable Brennan named Donnchadh O'Brennan, who was the Chief Poet of Ireland.

During the 16th and 17th centuries, the Brennan name became more widespread across Ireland. In 1659, the Petty's Census of Ireland listed several Brennan families living in counties such as Kilkenny, Waterford, and Cork.

A notable Brennan from the 18th century was Sir Jonah Brennan (1736-1801), an Irish physician and anatomist who served as the President of the Royal College of Surgeons in Ireland. In the 19th century, Michael Brennan (1827-1904) was a prominent Irish-American labor leader and politician in New York City.

Other historical figures with the Brennan surname include Theresa Brennan (1856-1939), an Irish-American philanthropist and founder of the Sisters of the Holy Child Jesus; and Louis Brennan (1852-1932), an Irish inventor and engineer who developed the first guided missile system.

Race and ethnic origin of people with the last name Brennan

We also have some data on the ancestry of people with the surname Brennan.

The below race categories are the modified race categories used in the Census Bureau's population estimates program. All people were categorized into six mutually exclusive racial and Hispanic origin groups:

1. White only
2. Black only
3. American Indian and Alaskan Native only
4. Asian and Pacific Islander only
5. Hispanic
6. Two or More Races

For the most recent 2010 census data, the race/ethnic origin breakdown for Brennan was:

Note: Any fields showing (S) means the data was suppressed for privacy so that the data does not in any way identify any specific individuals.

Since we have data from the previous census in 2000, we can also compare the values to see how the popularity of Brennan has changed in the 10 years between the two census surveys.

Data source

The last name data and ethnic breakdown of last names is sourced directly from the Decennial Census survey, conducted every 10 years by the United States Census Bureau.

The history and meaning of the name Brennan was researched and written by our team of onomatology and genealogy experts.

If you have a correction or suggestion to improve the history of Brennan, please contact us.

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