Kaius
Masculine
Kaius is a modern spelling of Caius, itself the older written form of Gaius — one of the handful of first names Roman men actually used, so common that scribes abbreviated it to a single letter C. It reached the New Testament in Greek, kept going through Latin into Portuguese and Italian, and arrives here with a K on the front and Kai sitting inside it, ready to be used.
How old is the name Kaius?
Kaius first appears in US birth records in 2005 — 20 years ago. The typical Kaius is a kid of about 5 — this name's wave is very recent. About 2,000 people named Kaius are estimated to be alive in the US today.
When was the name Kaius most popular?
Kaius peaked in 2020, reaching #1023 nationally. Today it ranks #1028, 5 places below that high. See the whole 2020 chart.
Kaius appears on this list:
Where it comes from
From Gaius to Kaius
The story of Kaius
The name begins as the Roman praenomen Gaius, in use for centuries before and after the Republic and written Caius as often as Gaius — in early Latin the two letters had not yet parted ways. Greek-speaking Christians carried it east as Gaios, and it turns up in the New Testament as the name of several ordinary men in the young church. Latin kept it alive through the medieval period: the sixteenth-century physician John Caius, co-founder of Gonville and Caius College in Cambridge, simply latinized his surname in the fashion of his time. The K spelling is recent and American, arriving on the charts only in this century, and it sits comfortably beside the independently popular Kai.
Meaningnot established
Not established
Roman praenomina are among the hardest names to translate, and Gaius is one of the least settled. A link to the Latin verb gaudere, 'to rejoice', has long been proposed but has never been established. What is documented is the name itself: Gaius and its variant spelling Caius were so ordinary in Rome that C. alone stood for it in inscriptions, and a Gaius is greeted by name in Paul's letter to the Romans and addressed in the Third Letter of John.
How the name formed
- Gaius
- Caius
- Gaios
- Caio
- Kaius
Related forms: Gaius · Caius · Caio · Gaio · Cayo · Gaios
Pronouncing Kaius
KY-us
KAY-us is also heard, and both are in genuine use — worth deciding early which one you will correct people to. The English college named for John Caius is pronounced 'keys', a survival with no bearing on how the given name is said today.
Nicknames for Kaius
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
- 2005
- Most boys named
- 2025216 — the highest on record
- Peak rank
- #1023reached in 2020
- Change vs 2024
- +16.1%216 in 2025, from 186
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.
Kaius in other languages
The same name elsewhere
- Gaius in Latin — same name
- Caius in Latin — spelling variant
- Caio in Portuguese — related form
- Gaio in Italian — related form
- Cayo in Spanish — related form
- Gaios in Greek — transliteration
Strongest US states over the last decade: Texas, California, Florida.
Kaiuss among us
people named Kaius are estimated to be alive in the US today
About 1 boy in 7,908 born in 2025 was named Kaius
Estimated from SSA birth records and published actuarial life tables. Method
Spellings of Kaius
- #1028
- Kaius on the 2025 chart
- #521
- counting every spelling
The SSA counts spellings, not names. Kaius went to 216 boys in 2025, but Caius and Khaius are the same name said out loud. Together the 3 spellings went to 475, which makes it the 521st most-given boys’ name of the year — 507 places above the chart.
- Caius254
- Kaius216
- Khaius5
About 1 boy in 3,596 born in 2025 was given one of these spellings — against 1 in 7,908 for Kaius itself.
Spellings are grouped by a fixed rule that folds interchangeable English spellings of one sound (ck/k, ph/f, x/ks, a non-initial y for i) and keeps vowels apart, so Sean and Shawn stay separate names. It errs towards splitting: a family here is never larger than the truth. SSA national data, 2025. Method
Is it right for you
What happens to a name after it peaks
The Keir test
Every popular name lives one long story — a climb, a peak, a slow settling back. Kaius's later chapters haven't been written yet, so we borrowed them: Keir climbed just as high around 1970, and its whole arc is on record. Line the two peaks up, and Keir's path sketches the road Kaius is walking now.
Kaius sits in the calm middle of the cycle — neither chasing a wave nor sliding off one. Middle-of-the-cycle names age slowly and predictably.
A scored estimate from 146 years of naming cycles — not a prophecy. Great names outlive statistics. How this is scored
Where Kaius is headed
Kaius should hold steady through 2030 — the curve is flat, and flat curves are the most predictable kind.
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.
Kaius beside its neighbors
The names ranked closest to Kaius in 2025, in babies rather than position — the bars are to scale.
US boys given each name in 2025.
The trade-off
- Comes with Kai already built in — a short form that is common, easy to spell and works on its own from the first day of school.
- A documented line back to Roman first names, and a New Testament bearer, which gives a very new spelling a very old spine.
- Recognizable across languages: Caio in Portuguese, Cayo in Spanish, Gaio in Italian all point back to the same name.
- Rare enough in American schools that a child is unlikely to share it, while the sound pattern is familiar rather than startling.
- Two pronunciations circulate, KY-us and KAY-us, and neither has won. Expect to say which one you use, politely, for years.
- The spelling will be guessed at. Caius, Cayus, Kaios and Kyus are all plausible to someone hearing it for the first time, and the K form is too new for people to default to it.
- Kai is so much easier to say that some people will shorten it without asking. That is fine if you like Kai, worth thinking about if you chose the longer name deliberately.
- This spelling's whole run is recent, so nearly everyone carrying it is a child. That will change as they grow, but for now it reads as a young name.
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What they receive
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Kaius
Masculine · #1028 in the U.S.
Frequently asked
- How many Kaiuss are there in the world?
- No country counts the world's names, so there is no worldwide figure — anyone quoting one is estimating. About 2,000 people named Kaius are estimated to be alive in the US today.
- How do you spell Kaius?
- Kaius is one of 3 recorded spellings. Caius is the more common one — 254 births in 2025 against 216 for Kaius.
- How popular is the name Kaius in 2025?
- Kaius ranks #1028 among US boy names in 2025, with 216 babies given the name.
- How rare is the name Kaius?
- About 1 in every 7,908 US boys born in 2025 was named Kaius — 216 in all.
- Will my child share the name Kaius with classmates?
- Kaius will almost certainly be the only one in school.
Ranked beside Kaius
Names sitting at a similar level of popularity right now.
Devon#1028 · Gatlin#1026 · Ivaan#1030 · Shai#1030 · Semaj#1026 · Yaseen#1030 · Kellan#1030 · Kooper#1024
Looking for what else is popular rather than what resembles Kaius? See the current top 100.
Choosing between Kaius and another name?
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US figures from the Social Security Administration. 1880–2025. Data & methodology
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