Caio
Masculine
Caio is the Portuguese and Italian form of Gaius, one of the handful of first names Roman men actually used — and one whose meaning the Romans themselves could not agree on.
How old is the name Caio?
Caio first appears in US birth records in 1990 — 35 years ago. The typical Caio is a kid of about 12 — this name's wave is very recent. About 700 people named Caio are estimated to be alive in the US today.
When was the name Caio most popular?
Caio peaked in 2023, reaching #3055 nationally. Today it ranks #3314, 259 places below that high. See the whole 2023 chart.
Lists built from the same records:
Where it comes from
From Gaius to Caio
The story of Caio
Republican Rome used about seventeen first names in all, and Gaius was the most common of them — abbreviated C. in inscriptions, which preserves the older spelling before the letter G was invented. Portuguese made Caio and Italian made Caio and Gaio. The name has been widely used in Brazil in recent decades. Welsh also has a Caio, a place name in Carmarthenshire, which is unconnected.
Meaningnot established
Not established
Gaius is among the oldest Roman first names and its origin is not established. A connection to a verb meaning to rejoice was offered in antiquity and is doubted; an Etruscan source has also been proposed. The name is certainly very old and certainly unexplained.
How the name formed
- Gaius
- Caio
Related forms: Gaius · Gaio · Cayo
Pronouncing Caio
KY-oo
Two syllables in Portuguese, running together. Italian says KA-yo, and English speakers often say KY-oh.
Nicknames for Caio
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
- 1990
- Most boys named
- 202340 — the highest on record
- Peak rank
- #3055reached in 2023
- Change vs 2024
- +16.7%35 in 2025, from 30
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.
Caio in other languages
The same name elsewhere
- Gaius in Latin — same name
- Gaio in Italian — same name
- Cayo in Spanish — same name
Strongest US states over the last decade: California, Florida, Massachusetts.
Caios among us
people named Caio are estimated to be alive in the US today
About 1 boy in 48,802 born in 2025 was named Caio
Estimated from SSA birth records and published actuarial life tables. Method
Spellings of Caio
- #3314
- Caio on the 2025 chart
- #860
- counting every spelling
The SSA counts spellings, not names. Caio went to 35 boys in 2025, but Kaio and Kayo are the same name said out loud. Together the 3 spellings went to 68, which makes it the 860th most-given boys’ name of the year — 2,454 places above the chart.
- Caio35
- Kaio22
- Kayo11
About 1 boy in 25,119 born in 2025 was given one of these spellings — against 1 in 48,802 for Caio 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 Ellijah test
Every popular name lives one long story — a climb, a peak, a slow settling back. Caio's later chapters haven't been written yet, so we borrowed them: Ellijah climbed just as high around 2008, and its whole arc is on record. Line the two peaks up, and Ellijah's path sketches the road Caio is walking now.
Caio 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 Caio is headed
Caio 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.
Caio beside its neighbors
The names ranked closest to Caio in 2025, in babies rather than position — the bars are to scale.
US boys given each name in 2025.
The trade-off
- One of the oldest documented Roman first names, in continuous written record for over two thousand years.
- Four letters, quick to write and easy to say.
- Very widely used in Brazil, so it has a large community behind it.
- The Portuguese, Italian and English pronunciations all differ.
- The meaning is genuinely unknown, which is unusual for a name this old and this well recorded.
- Cayo, Caio and Kaio all appear and none is standard in English.
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What they receive
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Caio
Masculine · #3314 in the U.S.
Frequently asked
- How many Caios are there in the world?
- No country counts the world's names, so there is no worldwide figure — anyone quoting one is estimating. About 700 people named Caio are estimated to be alive in the US today.
- How do you spell Caio?
- Caio is the most-used spelling in US records — 35 of the 68 babies given the name in 2025. The others recorded are Kaio and Kayo.
- How popular is the name Caio in 2025?
- Caio ranks #3314 among US boy names in 2025, with 35 babies given the name.
- How rare is the name Caio?
- About 1 in every 48,802 US boys born in 2025 was named Caio — 35 in all.
- Will my child share the name Caio with classmates?
- Caio will almost certainly be the only one in school.
Ranked beside Caio
Names sitting at a similar level of popularity right now.
Rainier#3314 · Coulter#3314 · Kaydon#3314 · Daksh#3314 · Kree#3314 · Calen#3314 · Karmello#3314 · Mathis#3314
Looking for what else is popular rather than what resembles Caio? See the current top 100.
Choosing between Caio and another name?
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US figures from the Social Security Administration. 1880–2025. Data & methodology
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