Caius
Masculine
Caius is the older Latin spelling of Gaius, one of the handful of first names that half of Rome seemed to share — so common that it was abbreviated to a single letter, C., on stone and in documents. It reached English through Roman history and through Shakespeare, who gave a Doctor Caius to The Merry Wives of Windsor and a disguise named Caius to Kent in King Lear. Two syllables, five letters, and a very long paper trail.
How old is the name Caius?
Caius first appears in US birth records in 1994 — 31 years ago. The typical Caius is a kid of about 6 — this name's wave is very recent. About 2,300 people named Caius are estimated to be alive in the US today.
When was the name Caius most popular?
Caius peaked in 2025, reaching #927 nationally. Today it ranks #927, exactly where it peaked. See the whole 2025 chart.
Lists built from the same records:
Where it comes from
From Gaius to Caius
The story of Caius
Caius and Gaius are the same Roman name written two ways — Latin C once stood for the g-sound, which is why the abbreviation for Gaius stayed C. long after spelling had moved on. It was among the most-used Roman first names for centuries, and it carried into Christian Europe with a third-century pope named Caius. In Tudor England the physician John Caius latinized his surname and, in the 1550s, refounded a Cambridge college that still bears it as Gonville and Caius — pronounced there, to this day, 'Keys'. The spelling also survives in Romance forms such as Portuguese Caio and Spanish Cayo, and in Stephenie Meyer's Twilight novels, where Caius is one of the Volturi elders.
Meaningnot established
Not established
Nobody has settled what Gaius/Caius originally meant. The proposal repeated most often connects it to Latin gaudere, 'to rejoice', but that link has never been established. What is documented is its role: one of the small set of Roman praenomina in constant use for centuries, so standard that the abbreviation C. was understood to mean Gaius.
How the name formed
- Gaius
- Caius
- Caio
Related forms: Gaius · Caio · Cayo · Gaio · Caius · Gaios
Pronouncing Caius
KY-us
KY-us is the common American reading; KAY-us is also heard, following the classical Gaius. The Cambridge college founded by John Caius is a separate tradition and says 'Keys' — worth knowing, not worth adopting unless you want it.
Nicknames for Caius
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
- 1994
- Most boys named
- 2025254 — the highest on record
- Peak rank
- #927reached in 2025
- Change vs 2024
- +23.3%254 in 2025, from 206
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.
Caius in other languages
The same name elsewhere
- Gaius in Latin — spelling variant
- Caio in Portuguese — same name
- Cayo in Spanish — same name
- Gaio in Italian — same name
- Caius in Romanian — same name
- Gaios in Greek — transliteration
Strongest US states over the last decade: California, Texas, Florida.
Caiuss among us
people named Caius are estimated to be alive in the US today
About 1 boy in 6,725 born in 2025 was named Caius
Estimated from SSA birth records and published actuarial life tables. Method
Spellings of Caius
- #927
- Caius on the 2025 chart
- #521
- counting every spelling
The SSA counts spellings, not names. Caius went to 254 boys in 2025, but Kaius 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 — 406 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 6,725 for Caius 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 Lucky test
Every popular name lives one long story — a climb, a peak, a slow settling back. Caius's later chapters haven't been written yet, so we borrowed them: Lucky climbed just as high around 1945, and its whole arc is on record. Line the two peaks up, and Lucky's path sketches the road Caius is walking now.
Caius 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 Caius is headed
Caius looks set to keep climbing gently, with roughly 15% 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.
Caius beside its neighbors
The names ranked closest to Caius in 2025, in babies rather than position — the bars are to scale.
US boys given each name in 2025.
The trade-off
- A documented record stretching from Roman antiquity through the papacy, Tudor Cambridge and Shakespeare — the spelling has never had to be reinvented.
- Short: two syllables, five letters, easy to write early.
- Travels as Caio, Cayo, Gaio and Gaius, so relatives in Romance-language families have a familiar form to reach for.
- Has ready-made short forms in Cai and Cy without depending on them.
- Two live pronunciations, KY-us and KAY-us, plus the Cambridge 'Keys'. You will be choosing one and correcting people for a while, at the doctor's office and on the first day of every school year.
- Expect the spelling to be guessed as Kaius, Cayus or Gaius. Saying the letters back is a lifelong small habit with this name.
- For some readers the first association is the Volturi elder in the Twilight books and films — a passing reference for most, but one that will come up.
- The Latin -us ending is distinct rather than neutral; it reads as classical, which some families love and others find heavier than they expected alongside a plain surname.
Nobody names a baby alone.
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What they receive
Someone added a name to your list
Caius
Masculine · #927 in the U.S.
Frequently asked
- How many Caiuss are there in the world?
- No country counts the world's names, so there is no worldwide figure — anyone quoting one is estimating. About 2,300 people named Caius are estimated to be alive in the US today.
- How do you spell Caius?
- Caius is the most-used spelling in US records — 254 of the 475 babies given the name in 2025. The others recorded are Kaius and Khaius.
- How popular is the name Caius in 2025?
- Caius ranks #927 among US boy names in 2025, with 254 babies given the name.
- How rare is the name Caius?
- About 1 in every 6,725 US boys born in 2025 was named Caius — 254 in all.
- Will my child share the name Caius with classmates?
- Caius will almost certainly be the only one in school.
Ranked beside Caius
Names sitting at a similar level of popularity right now.
Darian#927 · Dillon#929 · Halo#929 · Agastya#929 · Heath#929 · Isa#929 · Casper#924 · Neythan#924
Looking for what else is popular rather than what resembles Caius? See the current top 100.
Choosing between Caius and another name?
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US figures from the Social Security Administration. 1880–2025. Data & methodology
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