2000
#4,076
National surname rank
Recorded bearers 8,036
First available Census row
Per 100,000 2.98
Rare Last name
Hennessey
Anglicized form of the Irish surname Ó hAonghusa, meaning "descendant of Aonghus," derived from the Irish name meaning "one choice."
According to the 2020 US Census Bureau surname tables, roughly 8,860 Americans carry the last name Hennessey. That puts it at #4,451 in the national surname ranking, appearing at a frequency of 2.58 per 100,000 people (about 1 in 38,686 residents).
This page is the full Name Census profile for the Hennessey 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 Hennessey with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
8.9K
1 in 38,686
Census rank
#4,451
2020 decennial data
Per 100,000
2.6
Frequency rate
Recorded bearers
7.7K
rare in the US
Popularity narrative
The Census Bureau recorded 7,726 bearers of the surname Hennessey in its 2020 decennial surname file. At a rate of 2.58 per 100,000 residents, it holds the 4451st position in the national surname ranking.
Among Census respondents with the surname Hennessey, the largest self-reported group is White at 91.3%. The next largest groups are Hispanic (3.7%) and Two or More Races (3.1%).
Origin
Meaning and origin of Hennessey
The surname Hennessey originates from Ireland, where it emerged in the 16th century. It is an Anglicized form of the Irish Gaelic surname Ó hAonghusa, derived from the personal name Aonghus, meaning "one choice" or "one strength."
This name is believed to have originated in County Cork, where the Ó hAonghusa clan was based. The earliest recorded instances of the name appear in the Annals of the Four Masters, a chronicle of medieval Irish history compiled in the 17th century.
One notable early bearer of the name was Rory Hennessey, a 16th-century Irish chieftain who fought against English forces during the Tudor conquest of Ireland. Another historical figure was Bartholomew Hennessey, a 17th-century Catholic priest who was executed during the Cromwellian conquest of Ireland.
In the 18th century, the name Hennessey gained prominence with the success of the Hennessy Cognac brand, founded by Richard Hennessy, an Irish officer in the French army. The brand's popularity helped to spread the name throughout Europe and beyond.
Other notable individuals with the surname Hennessey include:
1. John Hennessey (1834-1912), an Irish-American entrepreneur and founder of the Hennessey & Ingalls advertising agency in Los Angeles.
2. John Francis Hennessey (1866-1939), an American politician who served as Governor of New Hampshire from 1917 to 1919.
3. Thomas Hennessey (1906-1979), an Australian rules footballer who played for the Carlton Football Club in the 1920s and 1930s.
4. Neil Hennessy (born 1952), an Irish-American businessman and founder of the Hennessy Funds investment firm.
5. John Hennessey (born 1964), an American automotive engineer and founder of Hennessey Performance Engineering, a company specializing in modifying high-performance vehicles.
The surname Hennessey has undergone various spelling variations over the centuries, including Hennessy, Henesey, and Hennesy. Some of these variations reflect regional pronunciations or attempts to Anglicize the name further.
Demographics
Ancestry and ethnicity for Hennessey
Among Census respondents with the surname Hennessey, the largest self-reported group is White at 91.3%. The next largest groups are Hispanic (3.7%) and Two or More Races (3.1%).
The bar chart below shows how Hennessey 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 Hennessey surname at the time of the 2020 Census, not any inherent property of the name itself.
- White91.3% · 7,057
- Hispanic or Latino3.7% · 283
- Two or more races3.1% · 243
- Asian and Pacific Islander0.9% · 73
- Black or African American0.8% · 62
- American Indian and Alaska Native0.1% · 8
Timeline
Historical Census data for Hennessey
Hennessey 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
#4,245
National surname rank
Recorded bearers 8,357
+321 bearers (+4.0%)
Per 100,000 2.83
Rank movement Down 169 places
2020
#4,451
National surname rank
Recorded bearers 7,726
-631 bearers (-7.6%)
Per 100,000 2.58
Rank movement Down 206 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #4,076 | 8,036 | 2.98 | First available Census row | First available Census row |
| 2010 | #4,245 | 8,357 | 2.83 | +321 bearers (+4.0%) | Down 169 places |
| 2020 | #4,451 | 7,726 | 2.58 | -631 bearers (-7.6%) | Down 206 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 Hennessey 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 | #4,245 | #4,451 | -4.9% |
| Count | 8,357 | 7,726 | -7.6% |
| Per 100K | 2.83 | 2.58 | -8.7% |
Between the 2010 and 2020 Census, the number of Hennessey bearers went from 8,357 to 7,726 (-7.6% change). The surname moved down 206 positions in the national ranking, going from #4,245 to #4,451.
FAQ
Hennessey surname: questions and answers
How many people in the U.S. have the surname Hennessey?
Name Census estimates that about 8,860 living Americans carry the surname Hennessey. Using the current population baseline, that works out to roughly 1 in 38,686 residents.
How common is Hennessey?
Hennessey ranks #4,451 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 2.58 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 7,726 people with the surname Hennessey. That is different from the site's living-bearer estimate (8,860), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 2.58 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 2.58 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 Hennessey.
Has Hennessey become more or less common over time?
Between 2010 and 2020, the surname Hennessey went from 8,357 recorded bearers to 7,726. That is a decrease of 631 (-7.6%). In the national ranking it fell from #4,245 to #4,451.
What does the Census say about the background of Hennessey?
Among Census respondents with the surname Hennessey, the largest self-reported group is White at 91.3%. The next largest groups are Hispanic (3.7%) and Two or More Races (3.1%). 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 Hennessey in the 2020 Census, accounting for 91.3% (7,057 people in the source table).
What is the full ancestry breakdown?
Hennessey appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (91.3%), Hispanic (3.7%), Two or More Races (3.1%). 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 Hennessey (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 Hennessey mean?
Anglicized form of the Irish surname Ó hAonghusa, meaning "descendant of Aonghus," derived from the Irish name meaning "one 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 Hennessey (2.58 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 many Americans have the surname Hennessey?
HowManyOfMe.org, our sister site, answers that with the living-bearer count in one glance.