Kaj
Masculine
Kaj is three letters and one syllable, and English speakers get it wrong almost every time. In Danish and Swedish the j is a y, so the whole name rhymes with eye — a single bright sound, gone as soon as it starts. It is an entirely ordinary name in Scandinavia and an entirely puzzling one everywhere else.
How old is the name Kaj?
Kaj first appears in US birth records in 1956 — 69 years ago. The typical Kaj alive today was born around 2006, making them about 19 years old. About 500 people named Kaj are estimated to be alive in the US today.
When was the name Kaj most popular?
Kaj peaked in 1969, reaching #3314 nationally. Today it ranks #12008, 8,694 places below that high. See the whole 1969 chart.
Where it comes from
From Caius to Kaj
The story of Kaj
Kaj has been in steady Danish use for centuries and is thoroughly domestic there, the sort of name that appears on shopfronts and in children's books without anyone thinking about where it came from. It is often assumed to be the same name as the Arthurian Kay — Sir Kay, King Arthur's foster brother, whose name is the Welsh Cai — but that is a separate line with a separate history, and the resemblance is coincidence rather than descent. American records hold Kaj in small numbers, carried by Danish and Swedish families and, more recently, by parents who want something very short and not from here.
Meaningnot established
Not established
Nothing about its origin is settled. The most common proposal derives it from the Roman praenomen Caius, itself of unknown meaning — the Romans had lost track of it too. Others connect it to a Frisian short form or to an old Danish word. None of these is demonstrated, and a name this short leaves very little evidence behind.
How the name formed
- Caius
- Kaj
Related forms: Kaj · Kai · Kai · Kay
Pronouncing Kaj
KYE
One syllable, rhyming with sky. Scandinavian j is always the English y, and here it closes a diphthong rather than starting a sound of its own. English readers meeting the name cold say KAJ with a hard j, which is the single most predictable thing about carrying it in America.
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
- 1956
- Most boys named
- 200620 — the highest on record
- Peak rank
- #3314reached in 1969
- Change vs 2024
- −66.7%5 in 2025, from 15
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.
Kaj in other languages
The same name elsewhere
- Kaj in Swedish — same name
- Kai in Finnish — spelling variant
- Kai in German — spelling variant
- Kay in Dutch — spelling variant
Kajs among us
people named Kaj are estimated to be alive in the US today
About 1 boy in 341,615 born in 2025 was named Kaj
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 Naman test
Every popular name lives one long story — a climb, a peak, a slow settling back. Kaj's later chapters haven't been written yet, so we borrowed them: Naman climbed just as high around 1948, and its whole arc is on record. Line the two peaks up, and Naman's path sketches the road Kaj is walking now.
Kaj 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
Kaj beside its neighbors
The names ranked closest to Kaj in 2025, in babies rather than position — the bars are to scale.
US boys given each name in 2025.
The trade-off
- Three letters and one syllable — about as compact as a name can be.
- It is completely standard in Denmark and Sweden, so it is a real name rather than a modern shortening.
- There is nothing to abbreviate, which some people find restful.
- The Kai spelling is well known in American use, so the sound is already familiar even where the letters are not.
- Almost every English speaker will say it wrong on sight, and the correction is required in every new room.
- It is regularly assumed to be initials or a typing error rather than a complete name.
- Kai is the spelling Americans know, and the family will be asked why they did not use it.
- Its origin cannot be given honestly, which is a real loss for a name that otherwise invites the question.
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What they receive
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Kaj
Masculine · #12008 in the U.S.
Frequently asked
- How many Kajs are there in the world?
- No country counts the world's names, so there is no worldwide figure — anyone quoting one is estimating. About 500 people named Kaj are estimated to be alive in the US today.
- How popular is the name Kaj in 2025?
- Kaj ranks #12008 among US boy names in 2025, with 5 babies given the name.
- How rare is the name Kaj?
- About 1 in every 341,615 US boys born in 2025 was named Kaj — 5 in all.
- Will my child share the name Kaj with classmates?
- Kaj will almost certainly be the only one in school.
Ranked beside Kaj
Names sitting at a similar level of popularity right now.
Garfield#12008 · Chas#12008 · Lew#12008 · Barney#12008 · Dewitt#12008 · Granville#12008 · Cicero#12008 · Willam#12008
Looking for what else is popular rather than what resembles Kaj? See the current top 100.
Choosing between Kaj and another name?
See them side by side — full stats, history and a gentle verdict.
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Your gut first, the numbers after — the split shows once you pick.
US figures from the Social Security Administration. 1880–2025. Data & methodology
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