2000
#70,473
National surname rank
Recorded bearers 259
First available Census row
Per 100,000 0.10
Very Rare Last name
Gilsenan
Anglicized form of the Gaelic surname Giolla Seanáin, meaning "servant/devotee of St. Senán".
According to the 2020 US Census Bureau surname tables, roughly 299 Americans carry the last name Gilsenan. That puts it at #78,873 in the national surname ranking, appearing at a frequency of 0.09 per 100,000 people (about 1 in 1,146,336 residents).
This page is the full Name Census profile for the Gilsenan 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 Gilsenan with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
299
1 in 1,146,336
Census rank
#78,873
2020 decennial data
Per 100,000
0.1
Frequency rate
Recorded bearers
261
very rare in the US
Popularity narrative
The Census Bureau recorded 261 bearers of the surname Gilsenan in its 2020 decennial surname file. At a rate of 0.09 per 100,000 residents, it holds the 78873rd position in the national surname ranking.
Among Census respondents with the surname Gilsenan, the largest self-reported group is White at 95.0%. The next largest groups are Two or More Races (3.4%) and Hispanic (1.1%).
Origin
Meaning and origin of Gilsenan
The surname Gilsenan is of Irish origin and is derived from the Gaelic personal name Gilla Seanáin, which means "servant or devotee of St. Senan". The earliest recorded examples of the name can be traced back to the early medieval period in Ireland.
The name Gilsenan is closely associated with County Clare, Ireland, where St. Senan founded a monastery on Scattery Island in the 6th century. Many of the early bearers of the name were likely followers or devotees of St. Senan, who lived and worked in the vicinity of his monastery.
One of the earliest recorded references to the name is found in the Annals of the Four Masters, a chronicle of medieval Irish history. The Annals mention a Gilladubh Gilsenan who was a distinguished scribe and learned man in the late 12th century.
In the 16th century, during the Tudor conquest of Ireland, a Gilsenan family held lands in the barony of Clanwilliam, County Tipperary. A notable member of this family was Edmond Gilsenan, who was appointed as the first Protestant Bishop of Raphoe in 1611.
Another prominent figure was Patrick Gilsenan, a distinguished Irish lawyer and judge who served as Lord Chief Justice of Ireland from 1677 to 1689. He played a significant role in the legal and political affairs of Ireland during the turbulent period of the Williamite Wars.
In the 18th century, Thomas Gilsenan, born in 1735, was a renowned Irish scholar and author. He published several works on Irish history and literature, including a translation of the ancient Irish epic, the Tain Bo Cuailnge.
The name Gilsenan has also been associated with various place names in Ireland, such as Gilsenanstown, a townland in County Tipperary, and Gilsenan's Lough, a lake in County Clare, named after the local Gilsenan family who owned lands in the area.
Demographics
Ancestry and ethnicity for Gilsenan
Among Census respondents with the surname Gilsenan, the largest self-reported group is White at 95.0%. The next largest groups are Two or More Races (3.4%) and Hispanic (1.1%).
The bar chart below shows how Gilsenan 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 Gilsenan surname at the time of the 2020 Census, not any inherent property of the name itself.
- White95.0% · 248
- Two or more races3.4% · 9
- Hispanic or Latino1.1% · 3
- Asian and Pacific Islander0.4% · 1
Timeline
Historical Census data for Gilsenan
Gilsenan 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
#71,678
National surname rank
Recorded bearers 272
+13 bearers (+5.0%)
Per 100,000 0.09
Rank movement Down 1,205 places
2020
#78,873
National surname rank
Recorded bearers 261
-11 bearers (-4.0%)
Per 100,000 0.09
Rank movement Down 7,195 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #70,473 | 259 | 0.10 | First available Census row | First available Census row |
| 2010 | #71,678 | 272 | 0.09 | +13 bearers (+5.0%) | Down 1,205 places |
| 2020 | #78,873 | 261 | 0.09 | -11 bearers (-4.0%) | Down 7,195 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 Gilsenan 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 | #71,678 | #78,873 | -10.0% |
| Count | 272 | 261 | -4.0% |
| Per 100K | 0.09 | 0.09 | -3.0% |
Between the 2010 and 2020 Census, the number of Gilsenan bearers went from 272 to 261 (-4.0% change). The surname moved down 7,195 positions in the national ranking, going from #71,678 to #78,873.
FAQ
Gilsenan surname: questions and answers
How many people in the U.S. have the surname Gilsenan?
Name Census estimates that about 299 living Americans carry the surname Gilsenan. Using the current population baseline, that works out to roughly 1 in 1,146,336 residents.
How common is Gilsenan?
Gilsenan ranks #78,873 in the 2020 Census surname tables and is classified on this site as "Very Rare." The Census recorded the name at a frequency of 0.09 per 100,000 residents, which is about 0 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 261 people with the surname Gilsenan. That is different from the site's living-bearer estimate (299), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.09 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.09 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 0 of them to have the surname Gilsenan.
Has Gilsenan become more or less common over time?
Between 2010 and 2020, the surname Gilsenan went from 272 recorded bearers to 261. That is a decrease of 11 (-4.0%). In the national ranking it fell from #71,678 to #78,873.
What does the Census say about the background of Gilsenan?
Among Census respondents with the surname Gilsenan, the largest self-reported group is White at 95.0%. The next largest groups are Two or More Races (3.4%) and Hispanic (1.1%). 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 Gilsenan in the 2020 Census, accounting for 95.0% (248 people in the source table).
What is the full ancestry breakdown?
Gilsenan appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (95.0%), Two or More Races (3.4%), Hispanic (1.1%). 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 Gilsenan (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 Gilsenan mean?
Anglicized form of the Gaelic surname Giolla Seanáin, meaning "servant/devotee of St. Senán". 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 Gilsenan (0.09 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 have the last name Gilsenan?
For a quick modern take, check how many people have the last name Gilsenan on our sister site HowManyOfMe.org.