Cillian
Masculine
Cillian is overwhelmingly a boys’ name — 4,084 boys against 6 girls since 1880.
Cillian is the Irish spelling of a name that left Ireland in the seventh century with a missionary monk, Cillian, who was killed at Würzburg and is still honored there as the city's patron. Germany kept him as Kilian, France as Killian, and Ireland held on to the original C. Spoken, it is three light syllables opening on a hard K.
How old is the name Cillian?
Cillian first appears in US birth records in 1995 — 30 years ago. The typical Cillian is a kid of about 3 — this name's wave is very recent. About 4,100 people named Cillian are estimated to be alive in the US today.
When was the name Cillian most popular?
Cillian peaked in 2024, reaching #463 nationally. Today it ranks #507, 44 places below that high. See the whole 2024 chart.
Cillian appears on these lists:
Works in Irish families too:
Where it comes from
From Cillín to Cillian
The story of Cillian
The name belongs to early Christian Ireland, the era of small stone churches and monks who kept traveling east. The best-documented bearer is the seventh-century Irish missionary Cillian, who preached in Franconia and was martyred at Würzburg around 689; his cult made the name a fixture in Bavaria, where it settled as Kilian and has been in continuous use ever since. French speakers took up Killian, and the K-spelling became the usual one in English too. Cillian, with its Irish C, is the form that stayed home longest — and it is the form that has recently begun traveling again, arriving in American records only in the last few decades and rising steadily since.
Meaningscholars disagree
Either 'church' with a small-thing ending, or 'sense, wisdom'
Two serious readings compete. One traces it to Old Irish cell, 'church' or 'monastic cell' (itself borrowed from Latin cella), plus the diminutive -án. The other traces it to Old Irish cíall, 'sense, sanity, wisdom'. Both are defensible on the linguistic evidence and neither has won.
How the name formed
- Cillín
- Cillian
- Killian
- Kilian
Related forms: Cillian · Killian · Kilian · Killian · Kiliaan · Cillín
Pronouncing Cillian
KIL-ee-an
The Irish C is always a hard K; there is no 's' sound in it. Three syllables in careful speech, often compressed to two in fast speech (KIL-yan). The stress stays on the first syllable in Irish, English and German alike.
Nicknames for Cillian
Moderate
What the data says
146 years of official birth records
The long climb, and where it stands now
The same years in position rather than babies
- First recorded
- 1995
- Most boys named
- 2024668 — the highest on record
- Peak rank
- #463reached in 2024
- Change vs 2024
- −10.9%595 in 2025, from 668
Rank is a position, a count is a headcount, and they move independently — a name can hold its rank while the number of babies behind it falls. Source: U.S. Social Security Administration.
Cillian in other languages
The same name elsewhere
- Cillian in Irish — same name
- Killian in English — spelling variant
- Kilian in German — spelling variant
- Killian in French — spelling variant
- Kiliaan in Dutch — related form
- Cillín in Irish — related form
Strongest US states over the last decade: New York, California, Texas. International figures from National Records of Scotland. Sources
Cillians among us
people named Cillian are estimated to be alive in the US today
About 1 boy in 2,871 born in 2025 was named Cillian
Estimated from SSA birth records and published actuarial life tables. Method
Is it right for you
What happens to a name after it peaks
The Bonnie test
Every popular name lives one long story — a climb, a peak, a slow settling back. Cillian's later chapters haven't been written yet, so we borrowed them: Bonnie climbed just as high around 1905, and its whole arc is on record. Line the two peaks up, and Bonnie's path sketches the road Cillian is walking now.
Cillian is climbing fast right now. Steep climbs tend to come with steep descents — the quicker a name arrives, the more firmly it belongs to its moment.
A scored estimate from 146 years of naming cycles — not a prophecy. Great names outlive statistics. How this is scored
Where Cillian is headed
Cillian looks set to keep climbing gently, with roughly 57% more babies a year by 2030 if the current curve holds.
Medium confidence — fitted on official counts through 2025.
A damped-trend projection of the official birth data — a sketch of momentum, not a promise. Every name's forecast, ranked.
Cillian beside its neighbors
The names ranked closest to Cillian in 2025, in babies rather than position — the bars are to scale.
US boys given each name in 2025.
The trade-off
- One pronunciation across Ireland, Britain, Germany and France — the sound does not shift when the name crosses a border.
- A documented record stretching back to a seventh-century Irish missionary, and continuous use in Bavaria ever since.
- The K-spellings, Killian and Kilian, are already familiar to English speakers, so the name reads as a name on first sight.
- Short, evenly stressed and easy for a child to say and write early.
- Rising in the United States and also charting in Scotland, so it is gaining recognition rather than losing it.
- The C will be read as an S by people who have not met the name: expect 'SILL-ee-an' from receptionists and substitute teachers, and expect to correct it politely for life.
- Cillian, Killian and Kilian all exist and all sound the same. Whichever you choose, the name will usually need spelling out over the phone.
- The obvious short form, Cill, sounds exactly like 'kill'. Most bearers simply use the full name, but it is better to notice this now than in a playground.
- It is climbing quickly in American records. A child born now is unlikely to share it in a classroom, but it will probably feel less unusual by the time they are grown.
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What they receive
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Cillian
Masculine · #507 in the U.S.
Frequently asked
- How many Cillians are there in the world?
- No country counts the world's names, so there is no worldwide figure — anyone quoting one is estimating. About 4,100 people named Cillian are estimated to be alive in the US today.
- How popular is the name Cillian in 2025?
- Cillian ranks #507 among US boy names in 2025, with 595 babies given the name.
- How rare is the name Cillian?
- About 1 in every 2,871 US boys born in 2025 was named Cillian — 595 in all.
- Will my child share the name Cillian with classmates?
- Cillian will almost certainly be the only one in school.
Ranked beside Cillian
Names sitting at a similar level of popularity right now.
Kyle#508 · Gunner#506 · Johnathan#508 · Pierce#505 · Ronin#504 · Leonidas#510 · Zaire#503 · Alonzo#511
Looking for what else is popular rather than what resembles Cillian? See the current top 100.
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US figures from the Social Security Administration; international figures from national statistics agencies. 1880–2025. Data & methodology
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