2000
#7,928
National surname rank
Recorded bearers 3,870
First available Census row
Per 100,000 1.43
Rare Last name
Koo
A Korean surname derived from the Chinese surname "Gu," meaning valley, ravine, or creek.
According to the 2020 US Census Bureau surname tables, roughly 5,895 Americans carry the last name Koo. That puts it at #6,365 in the national surname ranking, appearing at a frequency of 1.72 per 100,000 people (about 1 in 58,143 residents).
This page is the full Name Census profile for the Koo 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 Koo with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
5.9K
1 in 58,143
Census rank
#6,365
2020 decennial data
Per 100,000
1.7
Frequency rate
Recorded bearers
5.1K
rare in the US
Popularity narrative
The Census Bureau recorded 5,141 bearers of the surname Koo in its 2020 decennial surname file. At a rate of 1.72 per 100,000 residents, it holds the 6365th position in the national surname ranking.
Among Census respondents with the surname Koo, the largest self-reported group is Asian/Pacific Islander at 88.7%. The next largest groups are White (4.5%) and Two or More Races (3.7%).
Origin
Meaning and origin of Koo
The surname "Koo" is believed to have originated from China, specifically from the Guangdong and Fujian provinces, where it was commonly used during the Ming and Qing dynasties (1368-1912). The name is derived from the Chinese character "谷" (gǔ), which means "valley" or "small ravine." It is thought that the name was initially given to families who lived in or near valleys or small ravines.
Historical records indicate that the surname "Koo" can be traced back to the Song Dynasty (960-1279), where it appeared in various governmental and administrative documents. One notable mention is in the "Xingshi Hengyan" (行實衡眼), a historical text compiled during the Ming Dynasty, which lists several prominent "Koo" families from the Guangdong region.
The earliest recorded example of the name "Koo" is found in the "Jinshi Zhi" (金石志), a collection of inscriptions and writings from the Tang Dynasty (618-907). This text mentions a scholar named "Koo Yingzhi" (谷應之) who lived during the 8th century.
Throughout history, several notable individuals have borne the surname "Koo." For instance, Koo Hung-ming (1891-1965) was a renowned Chinese philosopher, writer, and diplomat during the early 20th century. Another significant figure was Koo Chen-fu (1888-1924), a prominent Chinese diplomat and politician who played a crucial role in the establishment of the League of Nations.
Other notable individuals with the surname "Koo" include Koo Kwang-mo (1892-1969), a Korean independence activist and politician; Koo Hui-sun (1914-1994), a South Korean politician and diplomat; and Koo Hee-je (1918-2001), a South Korean writer and academic.
It is worth noting that the surname "Koo" has also been associated with various place names and locations throughout China, such as Koo County (谷縣) in Henan Province and Koo Village (谷村) in Guangdong Province. These place names often reflect the geographical features of the region, further reinforcing the connection between the surname and its etymological roots.
While the surname "Koo" has a rich history and significance within Chinese and Korean cultures, it is important to recognize that this information is based on historical records and may not reflect the most up-to-date data or interpretations.
Demographics
Ancestry and ethnicity for Koo
Among Census respondents with the surname Koo, the largest self-reported group is Asian/Pacific Islander at 88.7%. The next largest groups are White (4.5%) and Two or More Races (3.7%).
The bar chart below shows how Koo 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 Koo surname at the time of the 2020 Census, not any inherent property of the name itself.
- Asian and Pacific Islander88.7% · 4,560
- White4.5% · 231
- Two or more races3.7% · 188
- Hispanic or Latino2.5% · 131
- Black or African American0.6% · 30
- American Indian and Alaska Native0.0% · 1
Timeline
Historical Census data for Koo
Koo 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
#6,843
National surname rank
Recorded bearers 4,923
+1,053 bearers (+27.2%)
Per 100,000 1.67
Rank movement Up 1,085 places
2020
#6,365
National surname rank
Recorded bearers 5,141
+218 bearers (+4.4%)
Per 100,000 1.72
Rank movement Up 478 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #7,928 | 3,870 | 1.43 | First available Census row | First available Census row |
| 2010 | #6,843 | 4,923 | 1.67 | +1,053 bearers (+27.2%) | Up 1,085 places |
| 2020 | #6,365 | 5,141 | 1.72 | +218 bearers (+4.4%) | Up 478 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 Koo 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 | #6,843 | #6,365 | 7.0% |
| Count | 4,923 | 5,141 | 4.4% |
| Per 100K | 1.67 | 1.72 | 3.0% |
Between the 2010 and 2020 Census, the number of Koo bearers went from 4,923 to 5,141 (+4.4% change). The surname moved up 478 positions in the national ranking, going from #6,843 to #6,365.
FAQ
Koo surname: questions and answers
How many people in the U.S. have the surname Koo?
Name Census estimates that about 5,895 living Americans carry the surname Koo. Using the current population baseline, that works out to roughly 1 in 58,143 residents.
How common is Koo?
Koo ranks #6,365 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 1.72 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 5,141 people with the surname Koo. That is different from the site's living-bearer estimate (5,895), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 1.72 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 1.72 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 Koo.
Has Koo become more or less common over time?
Between 2010 and 2020, the surname Koo went from 4,923 recorded bearers to 5,141. That is an increase of 218 (+4.4%). In the national ranking it rose from #6,843 to #6,365.
What does the Census say about the background of Koo?
Among Census respondents with the surname Koo, the largest self-reported group is Asian/Pacific Islander at 88.7%. The next largest groups are White (4.5%) and Two or More Races (3.7%). 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?
Asian/Pacific Islander is the largest self-reported group for the surname Koo in the 2020 Census, accounting for 88.7% (4,560 people in the source table).
What is the full ancestry breakdown?
Koo appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are Asian/Pacific Islander (88.7%), White (4.5%), Two or More Races (3.7%). 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 Koo (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 Koo mean?
A Korean surname derived from the Chinese surname "Gu," meaning valley, ravine, or creek. 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 Koo (1.72 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 Koo?
For a quick modern take, check how many people are called Koo on our sister site HowManyOfMe.org.