Cillian
Cillian was the 507th most popular name for boys in 2025, given to 595 babies. Its best year was 2024, when it ranked 463rd with 668 babies. Over the last ten years it has moved up 911 places. More babies were named Cillian in the 2020s than in any other decade.
Meaning Irish saint's name (meaning uncertain) · Irish
Say it KIL-ee-un /ˈkɪliən/
- Rank in 2025
- #507 boys, up 450 places since 2020
- Babies in 2025
- 595boys
- Girls and boys
- Almost always a boy’s name2021–2025
- Peak year
- 2024668 babies
- Total since 1880
- 4,090babies recorded
What does the name Cillian mean?
Cillian is an Irish saint's name. Wiktionary says it may come from ceallach, strife, or from ceall, a church or monastery cell, so its meaning is not settled. Killian and Kilian are anglicized spellings of the same name. The Irish C is always hard, so the name begins with a K sound. In the US the spelling Cillian has appeared only since the mid-1990s.
ceallach (Irish, “strife (proposed)”)ceall (Irish, “church, monastery (proposed)”)
How sure is this? Uncertain. Wiktionary offers 'strife' or 'church' without choosing.
Pronunciation: The C is always hard: KIL-ee-un, not SIL-ee-un.
Related names: Kilian, Killian, Cillín.
See also: Irish names.
Sources for this meaning
- Wiktionary, entry 'Cillian' (Irish section), Wiktionary (CC BY-SA 4.0; facts restated, no text reused)
- Wiktionary, entry 'Ceallach' (Irish section), Wiktionary (CC BY-SA 4.0; facts restated, no text reused)
- US Social Security Administration, national baby-name data 1880-2025 (yob*.txt), team3 computation of first year recorded, US Social Security Administration (public domain)
Cillian popularity since 1880
A few girls are given the name too: 6 since 2024.
| Year | Rank (boys) | Babies (boys) |
|---|---|---|
| 2025 | #507 | 595 |
| 2020 | #957 | 228 |
| 2010 | #2,359 | 54 |
| 2000 | — | — |
| 1990 | — | — |
| 1980 | — | — |
| 1970 | — | — |
| 1960 | — | — |
| 1950 | — | — |
| 1940 | — | — |
| 1930 | — | — |
| 1920 | — | — |
| 1910 | — | — |
| 1900 | — | — |
| 1890 | — | — |
| 1880 | — | — |
How popular is Cillian, counting every spelling?
Cillian is the most common spelling of a name family that ranked #506 for boys in 2025 once every spelling is counted together, compared with #507 for Cillian on its own. Together these spellings went to 595 boys in 2025.
| Spelling | Babies 2025 | Official rank | Babies 2021–2025 |
|---|---|---|---|
| Cillian | 595 | #507 | 2,434 |
Spellings count together when they sound the same in American English and are used for the same sex; nicknames and forms that sound different (such as Theo and Theodore) are kept apart. How we group spellings.
How many kids will share the name Cillian?
595 of the 3,606,400 babies born in the US in 2025 were named Cillian (0.17 per 1,000 births). For a boy named Cillian born in 2025, the chance that another child with the same name is in a class of 20 children the same age is under 1 in 50. If every grade liked the name as much as the 2025 babies do, only about one elementary school in 14 (of 430 pupils) would have a child named Cillian.
Shares of all registered births (NCHS); classes assumed to be children born the same year. How we estimate this.
How old are people named Cillian?
About 4,100 people born in the US named Cillian are alive today, with a median age of 4; half are between 2 and 9. That makes Cillian a young name: most people with it are children.
Babies given the name each year (SSA) times the share of that birth year still alive (SSA life tables). Counts people born in the US only. Method.
Cillian by state
How common Cillian was among boys born in each state in 2021–2025. It is notably more common than nationally in Massachusetts (3.0×), Connecticut (2.0×), Colorado (1.8×), New York (1.8×), Washington (1.7×). It is least common, relative to the national rate, in Iowa, Mississippi, Alabama.
Names with a similar history
These names rose and fell in step with Cillian: their share of US boys followed the most similar curve since 1880. If you like Cillian, they share its era and feel.
Middle names for Cillian · Sibling names for Cillian
Questions about the name Cillian
What does Cillian mean?
Cillian is usually explained as “Irish saint's name (meaning uncertain)”, but this is uncertain. Certainty: uncertain.
How popular is the name Cillian?
Cillian was the 507th most popular name for boys in 2025, given to 595 babies. Its best year was 2024, when it ranked 463rd with 668 babies. Over the last ten years it has moved up 911 places. More babies were named Cillian in the 2020s than in any other decade.
Is Cillian a boy or girl name?
In 2021–2025, almost always a boy’s name given the name Cillian in the US.
Where is Cillian most popular?
In 2021–2025, Cillian was most common in Alaska (0.84 per 1,000 boys), followed by Massachusetts and New Hampshire.