2000
#4,995
National surname rank
Recorded bearers 6,444
First available Census row
Per 100,000 2.39
Rare Last name
Mulcahy
Derived from the Irish Ó Maolchathaigh, meaning "descendant of a follower of Cathach," a personal name meaning "battle."
According to the 2020 US Census Bureau surname tables, roughly 7,415 Americans carry the last name Mulcahy. That puts it at #5,216 in the national surname ranking, appearing at a frequency of 2.16 per 100,000 people (about 1 in 46,224 residents).
This page is the full Name Census profile for the Mulcahy 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 Mulcahy with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
7.4K
1 in 46,224
Census rank
#5,216
2020 decennial data
Per 100,000
2.2
Frequency rate
Recorded bearers
6.5K
rare in the US
Popularity narrative
The Census Bureau recorded 6,466 bearers of the surname Mulcahy in its 2020 decennial surname file. At a rate of 2.16 per 100,000 residents, it holds the 5216th position in the national surname ranking.
Among Census respondents with the surname Mulcahy, the largest self-reported group is White at 92.6%. The next largest groups are Hispanic (3.2%) and Two or More Races (2.9%).
Origin
Meaning and origin of Mulcahy
The surname Mulcahy is of Irish origin, derived from the Old Irish Gaelic words "muileach" meaning "chieftain" or "leader" and "cath" meaning "battle". It is believed to have originated in County Cork, Ireland, during the 11th or 12th century.
The name is thought to have been first used to refer to a prominent leader or warrior in battle, and was likely bestowed as a descriptive surname to distinguish individuals of importance or military prowess. Over time, the name evolved into its current spelling, with various historical records showing variations such as Mulcahey, Mulcaghey, and Mulcaghie.
One of the earliest documented references to the name can be found in the Annals of Inisfallen, a medieval Irish chronicle compiled in the 12th century, which mentions a Mulcahy clan member named Domhnall Ó Muileacháin in the year 1171.
In the 16th century, the Mulcahy family held lands in the baronies of Muskerry and Duhallow in County Cork, and several members were noted for their involvement in the Desmond Rebellions against English rule in Ireland. Notable figures from this period include Donal Mulcahy, who fought alongside the Earl of Desmond in the Second Desmond Rebellion (1579-1583).
Another prominent Mulcahy was Tadhg Ó Muileacháin (c. 1600-1670), a renowned Irish poet and historian who composed works in both Irish and Latin, preserving valuable historical and genealogical information about the Gaelic families of Munster.
During the 17th and 18th centuries, the Mulcahy name was associated with several influential clergymen and scholars. Reverend Daniel Mulcahy (1718-1778) was a renowned Catholic priest and educator who established one of the earliest Catholic schools in Ireland after the Penal Laws were relaxed.
In more recent history, Riobárd Mulcahy (1886-1971) was a prominent Irish politician and military leader. He served as Chief of Staff of the Irish Republican Army during the Irish War of Independence and later became Minister for Defence and Minister for Education in the Irish Free State government.
Other notable individuals with the surname Mulcahy include John Vincent Mulcahy (1876-1942), an Irish-American businessman and politician who served as Mayor of Spokane, Washington, and Kathleen Mulcahy (1906-1976), an American author and playwright known for her works on Irish history and culture.
Demographics
Ancestry and ethnicity for Mulcahy
Among Census respondents with the surname Mulcahy, the largest self-reported group is White at 92.6%. The next largest groups are Hispanic (3.2%) and Two or More Races (2.9%).
The bar chart below shows how Mulcahy 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 Mulcahy surname at the time of the 2020 Census, not any inherent property of the name itself.
- White92.6% · 5,989
- Hispanic or Latino3.2% · 210
- Two or more races2.9% · 185
- Asian and Pacific Islander0.7% · 48
- Black or African American0.4% · 25
- American Indian and Alaska Native0.1% · 9
Timeline
Historical Census data for Mulcahy
Mulcahy 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
#5,279
National surname rank
Recorded bearers 6,595
+151 bearers (+2.3%)
Per 100,000 2.24
Rank movement Down 284 places
2020
#5,216
National surname rank
Recorded bearers 6,466
-129 bearers (-2.0%)
Per 100,000 2.16
Rank movement Up 63 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #4,995 | 6,444 | 2.39 | First available Census row | First available Census row |
| 2010 | #5,279 | 6,595 | 2.24 | +151 bearers (+2.3%) | Down 284 places |
| 2020 | #5,216 | 6,466 | 2.16 | -129 bearers (-2.0%) | Up 63 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 Mulcahy 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 | #5,279 | #5,216 | 1.2% |
| Count | 6,595 | 6,466 | -2.0% |
| Per 100K | 2.24 | 2.16 | -3.4% |
Between the 2010 and 2020 Census, the number of Mulcahy bearers went from 6,595 to 6,466 (-2.0% change). The surname moved up 63 positions in the national ranking, going from #5,279 to #5,216.
Notable bearers
Famous people with the surname Mulcahy
FAQ
Mulcahy surname: questions and answers
How many people in the U.S. have the surname Mulcahy?
Name Census estimates that about 7,415 living Americans carry the surname Mulcahy. Using the current population baseline, that works out to roughly 1 in 46,224 residents.
How common is Mulcahy?
Mulcahy ranks #5,216 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 2.16 per 100,000 residents, which is about 2 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 6,466 people with the surname Mulcahy. That is different from the site's living-bearer estimate (7,415), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 2.16 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 2.16 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 2 of them to have the surname Mulcahy.
Has Mulcahy become more or less common over time?
Between 2010 and 2020, the surname Mulcahy went from 6,595 recorded bearers to 6,466. That is a decrease of 129 (-2.0%). In the national ranking it rose from #5,279 to #5,216.
What does the Census say about the background of Mulcahy?
Among Census respondents with the surname Mulcahy, the largest self-reported group is White at 92.6%. The next largest groups are Hispanic (3.2%) and Two or More Races (2.9%). 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 Mulcahy in the 2020 Census, accounting for 92.6% (5,989 people in the source table).
What is the full ancestry breakdown?
Mulcahy appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (92.6%), Hispanic (3.2%), Two or More Races (2.9%). 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 Mulcahy (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 Mulcahy mean?
Derived from the Irish Ó Maolchathaigh, meaning "descendant of a follower of Cathach," a personal name meaning "battle." 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 Mulcahy (2.16 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 people are called Mulcahy?
Find out how common the surname Mulcahy is on our sister site HowManyOfMe.org — a quick modern estimate with the living-bearer count front and centre.