Caius
Caius was the 927th most popular name for boys in 2025, given to 254 babies. That is its highest rank since records began in 1880. Over the last ten years it has moved up 362 places. More babies were named Caius in the 2010s than in any other decade.
Meaning Origin uncertain · Latin
Say it KY-us /ˈkaɪəs/
- Rank in 2025
- #927 boys, up 282 places since 2020
- Babies in 2025
- 254boys
- Girls and boys
- Almost always a boy’s name2021–2025
- Peak year
- 2025254 babies
- Total since 1880
- 2,329babies recorded
What does the name Caius mean?
Caius is the old Latin spelling of Gaius, one of the most common Roman first names; early Latin used the letter C for both the k and g sounds. The origin of Gaius is uncertain: DMNES and Wiktionary both mention a possible link with Latin gaudere 'to rejoice'. Gaius was the name of several minor New Testament figures and the first name of Julius Caesar. Gonville and Caius College, Cambridge, is pronounced 'keys', after its founder John Caius, whose surname was Latinized from Kays.
Gaius / Caius (Latin, “Roman first name, perhaps related to gaudere 'rejoice'”)
How sure is this? Uncertain. Origin of Gaius uncertain; the 'rejoice' link is a suggestion.
Pronunciation: In classical Latin it was said GAH-yoos.
Related names: Gaius, Cai.
See also: Latin names.
Sources for this meaning
- Wiktionary, entry 'Caius' (Latin section), Wiktionary (Wikimedia Foundation)
- Wiktionary, entry 'Gaius' (Latin section), Wiktionary (Wikimedia Foundation)
- Dictionary of Medieval Names from European Sources (ed. S. L. Uckelman), Edition 2023 no. 1, s.v. 'Gaius', DMNES, Durham University
- Wikipedia, 'Caius', Wikipedia (Wikimedia Foundation)
Caius popularity since 1880
| Year | Rank (boys) | Babies (boys) |
|---|---|---|
| 2025 | #927 | 254 |
| 2020 | #1,209 | 156 |
| 2010 | #2,520 | 49 |
| 2000 | #6,382 | 10 |
| 1990 | — | — |
| 1980 | — | — |
| 1970 | — | — |
| 1960 | — | — |
| 1950 | — | — |
| 1940 | — | — |
| 1930 | — | — |
| 1920 | — | — |
| 1910 | — | — |
| 1900 | — | — |
| 1890 | — | — |
| 1880 | — | — |
How popular is Caius, counting every spelling?
Caius is a spelling of Kaius, a name family that ranked #599 for boys in 2025 once every spelling is counted together, compared with #927 for Caius on its own. Together these spellings went to 470 boys in 2025.
| Spelling | Babies 2025 | Official rank | Babies 2021–2025 |
|---|---|---|---|
| Kaius | 216 | #1,029 | 948 |
| Caius | 254 | #927 | 888 |
Spellings count together when they sound the same in American English and are used for the same sex; nicknames and forms that sound different (such as Theo and Theodore) are kept apart. How we group spellings.
How many kids will share the name Caius?
254 of the 3,606,400 babies born in the US in 2025 were named Caius (0.07 per 1,000 births). For a boy named Caius born in 2025, the chance that another child with the same name is in a class of 20 children the same age is under 1 in 50. If every grade liked the name as much as the 2025 babies do, only about one elementary school in 33 (of 430 pupils) would have a child named Caius.
Shares of all registered births (NCHS); classes assumed to be children born the same year. How we estimate this.
How old are people named Caius?
About 2,300 people born in the US named Caius are alive today, with a median age of 7; half are between 3 and 12. That makes Caius a young name: most people with it are children.
Babies given the name each year (SSA) times the share of that birth year still alive (SSA life tables). Counts people born in the US only. Method.
Caius by state
How common Caius was among boys born in each state in 2021–2025. It is notably more common than nationally in Minnesota (1.6×). In 25 states fewer than five boys a year got the name, too few for SSA to publish, so those states show as zero.
Names with a similar history
These names rose and fell in step with Caius: their share of US boys followed the most similar curve since 1880. If you like Caius, they share its era and feel.
Middle names for Caius · Sibling names for Caius
Questions about the name Caius
What does Caius mean?
The origin of Caius is uncertain: Origin of Gaius uncertain; the 'rejoice' link is a suggestion.
How popular is the name Caius?
Caius was the 927th most popular name for boys in 2025, given to 254 babies. That is its highest rank since records began in 1880. Over the last ten years it has moved up 362 places. More babies were named Caius in the 2010s than in any other decade.
Is Caius a boy or girl name?
In 2021–2025, almost always a boy’s name given the name Caius in the US.
Where is Caius most popular?
In 2021–2025, Caius was most common in Oklahoma (0.18 per 1,000 boys), followed by Minnesota and Wisconsin.