Head to head · Boys' names
Kasai vs Kenzo
#639 vs #628 in 2025
Kenzo is a whisker ahead (#628 vs #639 in 2025), but the curves point different ways: Kenzo is holding its place on the charts, Kasai is climbing the charts fast. On momentum, Kasai has the edge.
Cast your vote
Which one would you pick?
Your gut first, the numbers after — the split shows once you pick.
The tale of the tape
On the charts, Kenzo leads 5 measures of 6; Kasai leads 1.
Ranks, counts and years are measured in the official US birth record; the classroom and living figures are estimates computed from it. The dot marks the side each measure favours on the charts — more common, not better.
What the records say
146 years of US births, drawn on one scale
Two curves, one scale
Who owned which decade
- 1920s: Kasai —, Kenzo #3991 — Kenzo higher
- 1930s: Kasai —, Kenzo #3642 — Kenzo higher
- 1980s: Kasai —, Kenzo #6486 — Kenzo higher
- 1990s: Kasai #8445, Kenzo #8285 — Kenzo higher
- 2000s: Kasai #7815, Kenzo #5439 — Kenzo higher
- 2010s: Kasai #6205, Kenzo #1436 — Kenzo higher
- 2020s: Kasai #2046, Kenzo #570 — Kenzo higher
Kenzo stood higher in every recorded decade — 7 of 7.
Rank by decade
| Decade | Kasai | Kenzo |
|---|---|---|
| 1920s | — | #3991 |
| 1930s | — | #3642 |
| 1980s | — | #6486 |
| 1990s | #8445 | #8285 |
| 2000s | #7815 | #5439 |
| 2010s | #6205 | #1436 |
| 2020s | #2046 | #570 |
Average national rank across each decade. A dash means the name sat outside the recorded top of that decade.
The names themselves
Meaning, roots, sound and the people who carried each
Where each name comes from
Kasai
Not established
No settled meaning attaches to Kasai as a given name. What is documented is where the word already lives: the Kasai River and the Kasai provinces of the Democratic Republic of Congo, and, in Japan, the surname and place name Kasai — a district of eastern Tokyo and a city in Hyōgo Prefecture, written with several different sets of kanji depending on the family.
How it traveled
Kasai reached English speakers as a name on a map before it was a name for a child. The Kasai is a major river of Central Africa, long enough and important enough that the surrounding region and its provinces carry the name; European atlases print it as Kasaï, in the French spelling used across the Congo.
Kenzo
Commonly "strong/healthy" or "wise" plus "three" — often marking a third son
In Japanese the meaning is decided by the characters, not the sound. Kenzo is written many ways: 健三 with 健 "healthy, strong," 賢三 with 賢 "wise," 憲三 with 憲 "law," 建三 with 建 "to build." The final 三 means "three" and traditionally marked a third son, though it has long been used without that literal sense. Other spellings end in 蔵 or 造 instead. All are genuine Kenzos; no single reading owns the name.
How it traveled
The name is Japanese, and its structure is a very old pattern there: a meaningful first character joined to a number, so that the written form tells you something the spoken form does not. Romanized as Kenzo (properly Kenzō, with a long final vowel), it traveled outward in the twentieth century with Japanese emigration and with the people who carried it — among them the architect Kenzo Tange and the designer Kenzo Takada, who founded his Paris fashion house under the single name in 1970.
Where a reading is contested the note says so — this page does not turn a guess into a fact. The chain is each name's recorded forms, oldest first; the story is its opening, told in full on the name's own page.
Out loud, and in short
Kasai
kah-SIGH
Most American speakers land on two beats, kah-SIGH, with stress at the end. The Japanese name is three even beats, KAH-sah-ee, and the Congo river is often said kah-sah-EE. All are defensible, so whichever you choose you will be correcting people occasionally.
- Kas — The obvious first-syllable shortening; informal, not an inherited tradition, since the name is too new to have built one.
- Sai — Informal clipping of the back half; also stands alone as a given name in its own right.
- Kai — Used informally by families who want a one-syllable call name; a very well-established independent given name in the US.
Kenzo
KEN-zoh
Two syllables, stress on the first in American English. In Japanese the syllables are more evenly weighted and the final vowel is held longer — Ken-zoh-oh — which is what the macron in Kenzō marks. English speakers get it right on the first try either way.
- Ken — The obvious English short form, and a long-standing given name in its own right in both English and Japanese.
- Kenny — Informal, mostly used by family and in early childhood; also stands alone as a given name.
- Kenz — Casual and modern, mostly among peers rather than adults.
- Zo — Informal clipping from the back of the name; also heard as a short form of Alonzo and Enzo.
Is it right for you
The differences that decide it, laid out by what you want
Choose by what you want
Choose Kasai if you want…
- a name fewer children share#639 in 2025 — kasai will almost certainly be the only one in school
- a name on the way upup 1,828 places on the charts in five years
- a name that feels very nowKasai is climbing the charts fast
Choose Kenzo if you want…
- a name most people already know#628 in 2025, 445 babies that year
- a name holding steadyKenzo is holding its place on the charts
- a name that ages quietlyan estimated 40% chance of feeling dated by 2040, against 64% for Kasai
Each line is a measured difference between the two names — a rank, a count, a recorded form — never a judgement of either. Save the one that answers your question; it lands on your shortlist.
The trade-offs, name by name
Kasai
Strengths
- Only five letters and three plain vowels — people who hear it can usually spell it, and people who read it are close on the first try.
- Already exists as a real word on the map and in Japanese family registers, so it is a found name rather than a coined one.
- Sits alongside the well-worn Kai, Rai and Zai sounds, so it is unfamiliar as a whole without being unfamiliar in its parts.
To consider
- Stress and syllable count are genuinely unsettled: kah-SIGH, KAH-sah-ee and kah-sah-EE are all heard. Decide which one is yours early, because you will be the one teaching it.
- Said aloud in Japanese, kasai is also the ordinary word for a fire or blaze (火災) — written with different characters from the surname, but the same sound. Worth knowing if the family has Japanese ties.
- He will almost certainly be the only Kasai anywhere in his school, which means no ready-made familiarity: expect Kasey, Kai and Cassie as the usual near-misses on forms and roll calls.
Kenzo
Strengths
- Spelled exactly as it sounds in English, so it survives phone calls, forms and roll calls without correction.
- Ken and Kenny are ready-made short forms already familiar to English speakers, with Kenz and Zo available too.
- Works in both Japanese and English without adjustment — useful for a family living across the two.
To consider
- The English spelling drops the long vowel of Kenzō. If Japanese-speaking family matter to you, decide early which characters the name is written with, since that — not the romanization — is what carries the meaning.
- Kenzo is also a well-known Paris fashion label and fragrance line, so some adults will hear the brand before the name. It fades fast in a child's own social world, but it will come up.
- Because most American Kenzos are very young, older adults may not have met one before and will occasionally ask you to repeat it. One clear saying is usually enough.
Documented properties of each name — how it spells, travels and shortens — not opinions about the child.
How each is likely to age
Kasai
64%chance Kasai feels dated by 2040
Kasai 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.
Kenzo
40%chance Kenzo feels dated by 2040
Kenzo 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 reading of where each name sits on the long naming cycle — computed, not measured, and explained on the data page.
With your last name
Say both in full. The notes are facts about letters and sound — a rhyme, a shared initial, the monogram — not a verdict on either name.
Type a last name to hear Kasai and Kenzo in full.
Weighing the whole shortlist? Run the full comparison — up to eight names with your last name, initials, classroom projections and a printable report.
Decide together
Nobody names a baby alone
Still torn between Kasai and Kenzo?
Put both to the vote.
One link to your partner, your parents, your sister. Each of them gets the two names, a one-tap answer and room to say why — and every reply lands in one place.
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More than two in the running? Settle it with a bracket or run the full comparison with your last name.
More head-to-heads
Same measures, different pair. Sixty more are dealt daily in the arena.
Lists that carry both names
Every list here names both Kasai and Kenzo — the same style, ranked by the same records.
Kasai or Kenzo — the short answers
- Which is more popular, Kasai or Kenzo?
- Kenzo, in 2025: Kenzo ranked #628 with 445 babies; Kasai ranked #639 with 437 babies.
- Which name is rising faster, Kasai or Kenzo?
- Kasai. Over the last five years Kasai moved up 1,828 places; Kenzo moved down 80 places.
- Which is the older name, Kasai or Kenzo?
- Kasai entered the US charts in 1996; Kenzo entered the US charts in 1920. On the American record, Kenzo is the older name.
- How many people are named Kasai and Kenzo?
- About 1,100 people named Kasai are estimated to be alive in the US today. About 4,600 people named Kenzo are estimated to be alive in the US today.
- Will there be other Kasais or Kenzos in the classroom?
- Kasai will almost certainly be the only one in school. Kenzo will almost certainly be the only one in school.
US figures from the Social Security Administration, 1880–2025. Votes are battle voters on this site, not the birth record. Data & methodology
Keep playing
Sixty more head-to-heads are dealt in the arena every day — or line up Kasai, Kenzo and the rest of your shortlist with your last name in one printable report.
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