2000
#3,550
National surname rank
Recorded bearers 9,187
First available Census row
Per 100,000 3.41
Uncommon Last name
Hennessy
Derived from the Irish Ó hAonghusa, meaning "descendant of Aonghus," a personal name composed of Celtic elements meaning "one" and "choice."
According to the 2020 US Census Bureau surname tables, roughly 10,381 Americans carry the last name Hennessy. That puts it at #3,821 in the national surname ranking, appearing at a frequency of 3.03 per 100,000 people (about 1 in 33,017 residents).
This page is the full Name Census profile for the Hennessy surname. You will find the Census Bureau frequency data, a multi-census history view, an ancestry and ethnicity breakdown based on self-reported demographics, the name's meaning and origin where available, and answers to the most common questions people ask about this surname.
For British records, Name Census UK has a British surname profile for Hennessy with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
10K
1 in 33,017
Census rank
#3,821
2020 decennial data
Per 100,000
3.0
Frequency rate
Recorded bearers
9.1K
uncommon in the US
Popularity narrative
The Census Bureau recorded 9,053 bearers of the surname Hennessy in its 2020 decennial surname file. At a rate of 3.03 per 100,000 residents, it holds the 3821st position in the national surname ranking.
Among Census respondents with the surname Hennessy, the largest self-reported group is White at 92.1%. The next largest groups are Hispanic (3.4%) and Two or More Races (3.0%).
Origin
Meaning and origin of Hennessy
The surname Hennessy originated in Ireland. It is an Anglicized version of the Irish Gaelic name Ó hAonghusa, which means "descendant of Aonghus." The name Aonghus is derived from the old Irish word "oan," meaning "one," and the word "gus," meaning "choice" or "excellent."
The earliest recorded instances of the Hennessy surname date back to the 13th century in County Cork, Ireland. It is believed that the name originated in the Gaelic-speaking region of West Munster, particularly in the baronies of Muskerry and Duhallow.
In the Annals of the Kingdom of Ireland by the Four Masters, a historical chronicle written in the 17th century, there are several references to the Hennessy family and their involvement in various conflicts and battles during the medieval period.
One of the earliest known individuals with the surname Hennessy was Phillip Hennessy, who was born in County Cork around 1480. He was a prominent landowner and chieftain of the Hennessy clan in the region.
In the 16th century, the Hennessy family played a significant role in the Desmond Rebellions, which were a series of uprisings against English rule in Ireland. Sir John Hennessy (c. 1530-1598) was a notable figure during this period, leading the Hennessy clan in support of the rebel forces.
Another prominent individual from this era was Richard Hennessy (c. 1590-1650), who was a member of the Irish Parliament and a staunch supporter of Catholic rights during the Irish Confederate Wars.
During the 17th and 18th centuries, many members of the Hennessy family were forced to leave Ireland due to the Penal Laws and the suppression of Catholic landowners. Some settled in other parts of Europe, such as France, where they established the famous Hennessy cognac brand.
Notable individuals with the Hennessy surname include:
1. Richard Hennessy (1724-1800), the founder of the Hennessy cognac distillery in France.
2. John Pope Hennessy (1834-1891), an English writer and biographer.
3. James Hennessy (1837-1916), an Irish businessman and politician who served as a Member of Parliament.
4. Brendan Hennessy (1905-1959), an Irish playwright and novelist.
5. John Hennessy (born 1952), an American computer scientist and the 10th President of Stanford University.
Demographics
Ancestry and ethnicity for Hennessy
Among Census respondents with the surname Hennessy, the largest self-reported group is White at 92.1%. The next largest groups are Hispanic (3.4%) and Two or More Races (3.0%).
The bar chart below shows how Hennessy bearers described their own race and ethnicity on the 2020 Census form. The Census Bureau groups responses into six broad categories: White, Black or African American, Hispanic or Latino, Asian and Pacific Islander, American Indian and Alaska Native, and Two or More Races. When a category has too few respondents for a given surname, the Bureau suppresses the figure to protect individual privacy, which is why some names show fewer than six slices.
Percentages are shown for every Census year so the breakdown stays comparable over time. When the source file also includes raw headcounts, Name Census shows those alongside the percentages in the legend.
Keep in mind that these are self-reported numbers. A person's surname does not determine their race or ethnicity, and the distribution you see here reflects the specific population who happened to carry the Hennessy surname at the time of the 2020 Census, not any inherent property of the name itself.
- White92.1% · 8,341
- Hispanic or Latino3.4% · 309
- Two or more races3.0% · 271
- Asian and Pacific Islander0.7% · 67
- Black or African American0.6% · 57
- American Indian and Alaska Native0.1% · 8
Timeline
Historical Census data for Hennessy
Hennessy appears in 3 published Census surname files: 2000, 2010, 2020. The cards below show how the name's rank and bearer count changed across each release.
2010
#3,790
National surname rank
Recorded bearers 9,338
+151 bearers (+1.6%)
Per 100,000 3.17
Rank movement Down 240 places
2020
#3,821
National surname rank
Recorded bearers 9,053
-285 bearers (-3.1%)
Per 100,000 3.03
Rank movement Down 31 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #3,550 | 9,187 | 3.41 | First available Census row | First available Census row |
| 2010 | #3,790 | 9,338 | 3.17 | +151 bearers (+1.6%) | Down 240 places |
| 2020 | #3,821 | 9,053 | 3.03 | -285 bearers (-3.1%) | Down 31 places |
For 2020, the Census Bureau published race and Hispanic-origin columns as counts rather than percentages. Name Census converts those counts back into shares so the ancestry section stays comparable with the older surname files.
Year on year
2010 vs 2020 Census
How has the Hennessy surname changed between Census years? The chart shows bearer count side by side, and the table compares rank, count, and frequency.
Census year comparison
20102020
| Metric | 2010 | 2020 | Change |
|---|---|---|---|
| Rank | #3,790 | #3,821 | -0.8% |
| Count | 9,338 | 9,053 | -3.1% |
| Per 100K | 3.17 | 3.03 | -4.5% |
Between the 2010 and 2020 Census, the number of Hennessy bearers went from 9,338 to 9,053 (-3.1% change). The surname moved down 31 positions in the national ranking, going from #3,790 to #3,821.
Notable bearers
Famous people with the surname Hennessy
FAQ
Hennessy surname: questions and answers
How many people in the U.S. have the surname Hennessy?
Name Census estimates that about 10,381 living Americans carry the surname Hennessy. Using the current population baseline, that works out to roughly 1 in 33,017 residents.
How common is Hennessy?
Hennessy ranks #3,821 in the 2020 Census surname tables and is classified on this site as "Uncommon." The Census recorded the name at a frequency of 3.03 per 100,000 residents, which is about 3 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 9,053 people with the surname Hennessy. That is different from the site's living-bearer estimate (10,381), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 3.03 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 3.03 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 3 of them to have the surname Hennessy.
Has Hennessy become more or less common over time?
Between 2010 and 2020, the surname Hennessy went from 9,338 recorded bearers to 9,053. That is a decrease of 285 (-3.1%). In the national ranking it fell from #3,790 to #3,821.
What does the Census say about the background of Hennessy?
Among Census respondents with the surname Hennessy, the largest self-reported group is White at 92.1%. The next largest groups are Hispanic (3.4%) and Two or More Races (3.0%). These figures come from the 2020 Census Bureau surname tables, based on how respondents described their own race and ethnicity.
Which group reports this surname most often?
White is the largest self-reported group for the surname Hennessy in the 2020 Census, accounting for 92.1% (8,341 people in the source table).
What is the full ancestry breakdown?
Hennessy appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (92.1%), Hispanic (3.4%), Two or More Races (3.0%). For 2020, the source file also published raw headcounts for each group, which is why this page can show both percentages and counts in the ancestry section.
Is this page using the latest Census data?
Yes. This page is using the latest surname file currently loaded on Name Census, which is 2020. The historical section above also keeps any older Census surname entries we have for Hennessy (2000, 2010, 2020).
Does the Census include every surname?
No. The Census Bureau only publishes surnames that appeared at least 100 times in a given decennial Census. That means very rare surnames are excluded entirely, and a surname can appear in one Census release but disappear from a later one if it falls below the reporting threshold.
Why don't the ancestry percentages always add up to exactly 100%?
There are two main reasons: rounding and suppression. The Census Bureau rounds published values, and it may suppress very small cells to protect privacy. For 2020, the Bureau also published raw group counts rather than direct percentages, so Name Census converts those counts back into shares for comparability across census years.
What does Hennessy mean?
Derived from the Irish Ó hAonghusa, meaning "descendant of Aonghus," a personal name composed of Celtic elements meaning "one" and "choice." The fuller origin note on this page goes into more detail.
Where does the surname data come from?
All surname statistics on Name Census are drawn from the US Census Bureau's decennial surname frequency tables. These files list every surname that appeared 100 or more times in the 2020 Census, along with a count, a per-100,000 rate, and a self-reported demographic breakdown. You can read the full explanation on our methodology page.
How does Name Census estimate living bearers?
For surnames, Name Census does not age cohorts the way it does for first names. Instead, it takes the Census Bureau's published frequency for Hennessy (3.03 per 100,000) and applies that rate to the current U.S. resident population to estimate how many living Americans have the surname today.
How common is the surname Hennessy?
You can see how many people are called Hennessy on our sister site HowManyOfMe.org — same data roots, lighter UI.