This article looks at how common Brennan is as a last name in Ireland and the United States from the 19th century to the present day.
You’ll learn the meaning and origins of the Brennan surname while exploring some notable and famous people that held it.
I use census records, emigration lists, and military archives to uncover fascinating patterns. If you’re studying your genealogy, check out my sources at the end of the post so you can do your own research.
How Common Is Brennan As A Surname In Ireland?
Ireland does not disclose current statistics on surnames in much detail. The most that we get is the top ten last names in birth registrations for the previous year. Brennan isn’t as common as that!
However, an Irish genealogist studied the top one hundred surname numbers in Ireland between 1992 and 1997. Seán Murphy based his research on telephone books. This isn’t as accurate as a census but gives a good approximation.
Brennan was ranked 26 in the top one hundred names in this decade with a total of 19,100 entries.
This graphic shows how it ranks compared to the 1st, 33rd, 66th, and 100th entries in the survey:
Brennan In The Early 1900s
The Irish have traditionally emigrated to Britain, the U.S., Canada, and Australia in recent centuries. They were driven by various factors like political upheaval, scarcity of work, and food deprivation.
The largest wave of emigration to the United States occurred during the 19th century. The peak was in response to the Great Irish Famine, which took place between 1845 and 1852. A plant disease devastated the main food and income crop for much of the population.
So, let’s focus on the early 1900s.
I used online archives to calculate the total numbers by surname. I consider these estimates due to some percentage of transcription errors. So, I’ve rounded the numbers to the nearest fifty.
There were 14,600 residents named Brennan on the island in 1911.
Ten years earlier, Brennan had about 14,650 residents in the 1901 census.
Population Estimates In The 1890s
A study of Irish surnames was conducted in 1890 by the head of the Civil Registrations Office. It was published as a “Special Report on Surnames In Ireland.”
The survey estimated that there were about 16,000 people named Brennan in the country.
Emigration To America After The Irish Famine
The Irish have traditionally emigrated to Britain, the U.S., Canada, and Australia in recent centuries. They were driven by various factors like political upheaval, scarcity of work, and food deprivation.
The largest wave of emigration to the United States occurred during the 19th century. The peak was in response to the Great Irish Famine, which took place between 1845 and 1852. A plant disease devastated the main food and income crop for much of the population.
I studied the Brennan name in the shipping passenger lists arriving in New York during this period. The departures were from both Ireland and England.
This picture shows how the numbers rose and fell in the years after the famine.
Estimating Rank In The United States
The United States publishes high-level details from the 2010 census that includes the totals of surnames with over one hundred bearers.
I reviewed the list to identify which names are predominantly Irish in origin to provide an estimate of the rankings of Irish names in the United States.
Historically, some Irish families with Gaelic surnames took English-sounding names as translations under the influence of colonization.
As these names also have English origins, they will have been brought to the United States by both British and Irish immigrants. Because the census doesn’t ask about specific European origin (e.g. England vs Ireland), it’s impossible to identify the proportion with Irish heritage.
For the purpose of this website, I’ve mostly excluded names that have varying origins when considering “Irish” names in the U.S. censuses.
With that explanation out of the way, let’s look at how Brennan ranks in America.
How Common Is Brennan As A Last Name In The United States?
Based on the 2010 U.S. census, the name Brennan ranks about 701 among Irish names in America with 49,238 bearers.
Brennan In Historic Census Years
It is fascinating to examine how the prevalence of a surname shifts over the course of time in a country as young as the United States. As well as immigration, this reflects other demographic shifts across the nation. Factors include higher child mortality rates and longer life expectancy.
The historic census records have been transcribed and digitized. I used online archives to run counts of surname populations.
But the totals can’t be exactly accurate due to transcription errors. So, I’ve rounded the numbers to the nearest 50 in the graph below.
This picture shows the numbers every twenty years from 1860 to 1940.
These are the numbers in the graph:
- 1860: 4,350
- 1880: 12,000
- 1900: 18,750
- 1920: 22,850
- 1940: 28,500
Brennan In World War II
About 8.3 million men and women enlisted in the U.S. Army during the Second World War. Many were of Irish heritage, and some were born in Ireland.
I found registration records for 1,957 soldiers named Brennan who enlisted between 1938 and 1946.
There were 43 who were born in Ireland.
Brennan Surname: Meaning And Origin
Two Gaelic surnames were anglicized to Brennan: Ó Braonáin and Mac Brannain.
Ó Braonáin (descendant of Braonán) is derived from the Gaelic word “braon” which refers to a teardrop or a state of sorrow. Mac Brannain means son of Brannan, with Brannan meaning a raven.
A notable early Brennan clan were chieftains of Ossory, an area that now spans the counties of Kilkenny and Laois. A Kerry branch of Brennans were allies of the powerful O’Sullivan Mór clan.
Famous Or Historic People Named Brennan
Here are some notable people with the family name:
- Louis Brennan (1852-1932): noted inventor who emigrated from Ireland to Australia and invented a guided missile known as the Brennan torpedo.
- Maeve Brennan (1917-1993): moved to the U.S. when her father Robert was appointed as Ireland’s first ambassador and became a noted columnist and short story writer with the New Yorker.
Sources
External Research
The Ireland 1990s estimates are from Seán J. Murphy’s research paper.
The population estimates of 1890 are based on the “Special Report on Surnames in Ireland“, published in 1909.
The population figures for the 2010 U.S. Census come from a file provided by the U.S. Census Bureau.
Internal Research
Some of the population numbers are based on my own research and calculations using online archives. I’ve rounded those numbers to the nearest 50 to account for transcription errors and other technical issues with online databases of this type.
The Irish census estimates for 1901 and 1911 are my calculations based on the Irish National Archives
I plotted the emigration figures from 1845 to 1854 based on calculations from the archives of the New York Passenger Lists (1820-1957).