Kastor
A masculine Greek name meaning "excelling", derived from the Greek word "kastor".
Name Census estimates that about 10 living Americans carry the first name Kastor. The name is used almost exclusively for boys. The average person named Kastor today is around 7 years old, and the year with the single highest number of Kastor births was 2017 (5 babies).
This page is the full Name Census profile for Kastor. Below you will find a gender breakdown showing how the name splits between male and female registrations, a year-by-year popularity chart stretching back to 1880, decade-level totals, the top US states for this name, its meaning and etymology, and a set of frequently asked questions with data-backed answers.
Key insights
- • Fewer than 100 living Americans are believed to carry the name Kastor. It is among the rarest names in the SSA records.
People living today
10
~ 1 in 34,275,434 Americans
Peak year
2017
5 babies that year
Average age
7
years old
2021 SSA rank
#13,110
Tracked since 2017
Popularity
Kastor: popularity over time
The SSA tracks Kastor from the 2010s through to the 2020s, spanning 2 decades of birth certificate data. The biggest single decade for the name was the 2020s, with 5 total registrations. The name continues to be given at rates close to its all-time high, suggesting it has not yet fallen out of fashion.
Babies born per year
Decades
Kastor by decade
The table below breaks the full SSA timeline into ten-year windows. Each row shows how many male and female babies were given the name Kastor during that decade, along with a combined total. This is useful for spotting eras where the name surged or retreated.
Origin
Meaning and history of Kastor
The name Kastor has its origins in ancient Greek mythology and culture, dating back to the classical era of ancient Greece. It is derived from the Greek word "kastor," which means "beaver." The name was borne by one of the twin brothers in Greek mythology, Kastor and Polydeukes, who were known as the Dioskouroi or the "sons of Zeus."
Kastor and his twin brother Polydeukes were the offspring of Leda and the god Zeus, who had taken the form of a swan to seduce her. According to the myth, Kastor was mortal, while Polydeukes was immortal. They were renowned for their strength and bravery and were frequently depicted as horsemen in ancient Greek art and literature.
The earliest recorded instance of the name Kastor can be found in Homer's epic poems, the Iliad and the Odyssey, which date back to the 8th century BC. In these works, Kastor and Polydeukes are portrayed as heroes who fought alongside the Achaeans in the Trojan War.
Throughout history, several notable figures have borne the name Kastor. One of the earliest was Kastor of Rhodes, a renowned Greek scholar and grammarian who lived in the 1st century BC. Another famous Kastor was Kastor of Massalia (modern-day Marseille), a Greek explorer and navigator who founded the colony of Massalia in the 6th century BC.
In the realm of ancient philosophy, Kastor of Pergamon was a renowned Stoic philosopher who lived in the 2nd century AD. He was a student of the famous Stoic teacher Musonius Rufus and wrote extensively on ethics and logic.
During the Byzantine era, Kastor was the name of a celebrated poet and hymnographer who lived in the 6th century AD. Known as Kastor the Hymnographer, he composed numerous liturgical hymns and is celebrated as a saint in the Eastern Orthodox Church.
Another notable figure with the name Kastor was Kastor Agrippa, a Roman historian and military leader who lived in the 1st century AD. He served as a general under the Roman emperor Nero and wrote a history of the Roman Empire, which has unfortunately been lost to time.
These examples illustrate the rich history and cultural significance of the name Kastor, which has been borne by scholars, philosophers, explorers, and military leaders throughout the ancient world. The name's association with the mythological twin heroes Kastor and Polydeukes has endured for over two millennia, cementing its place in the annals of Western civilization.
People
Kastor + last name combinations
How many people share a full name with Kastor as the first name? Click a combination below to see the estimate, or search any pairing.
Related
Other names starting with K
Other first names starting with K with a similar number of bearers.
FAQ
Kastor: questions and answers
How many people in the U.S. are named Kastor?
Name Census puts the figure at roughly 10 living Americans. We arrive at this by taking every SSA birth registration for Kastor going back to 1880 and adjusting each cohort for expected survival using CDC actuarial life tables. The result is an age-weighted living-bearer count, not a raw birth total. That works out to about 1 in 34,275,434 US residents.
Is Kastor a common name?
We classify Kastor as "Very Rare". It ranks above 28.5% of all first names in the SSA dataset by living bearers. Across the full history of the data, 10 babies have been registered with this name.
When was Kastor most popular?
The single biggest year for Kastor was 2017, when 5 babies received the name. The fact that the average living Kastor is about 7 years old gives you a rough sense of which era contributed the most bearers who are still alive today.
What does the SSA popularity chart show?
The chart tracks births, not the number of people alive with the name today. Each point shows how many babies were given the name Kastor in that year. That makes it useful for spotting when the name rose, peaked, or faded.
Is Kastor a male name?
Yes, 100.0% of people registered as Kastor in the SSA data are male. You can see the full per-sex comparison in the gender distribution section above, which includes the latest year rank, birth count, and peak year for each sex.
Is Kastor still being used today?
Yes. The SSA still recorded Kastor in 2024, and the page above shows its latest-year rank where available. A name can be well past its peak and still remain in steady use, especially if it built up a large population over earlier decades.
Why can a name have a lot of living bearers even if it is not trendy now?
Because living-bearer counts and current baby-name popularity measure different things. A name like Kastor can build up a very large population over many decades, even if fewer parents are choosing it now than they did at its peak.
Where does this data come from?
First-name figures come from the Social Security Administration's national baby name files, which cover every name on a birth certificate from 1880 to 2024. Living-bearer estimates layer in CDC actuarial life tables broken out by sex to account for mortality. The population baseline (342,754,338) is the Census Bureau's latest national estimate. You can read the full calculation on our methodology page.
Does every first name have Census demographic data?
No. The public Census first-name release only covers names that met the Bureau's publication rules, so many rarer names in the SSA files do not have a published Census demographic snapshot. In those cases, the page still shows the SSA trend, gender history, and state data.
How many people are called Kastor?
HowManyOfMe.org, our sister site, answers that with the living-bearer count in one glance.