An estimated 4,051 living Americans are named Cillian.
How rare is Cillian?
Cillian is moderately uncommon among babies today, with 595 boys receiving the name in 2025, down 10.9% from its 2024 peak.
How old is the typical Cillian?
The median age of a living American named Cillian is approximately 4 years, with most bearers falling between 2 and 9 years old.
Is Cillian still popular?
Yes — Cillian is currently rising in popularity, with 595 births in 2025. Births this decade are running about 5.1× higher than the previous decade.
Where is Cillian most common?
Cillian has its strongest geographic signal in Massachusetts, where it appears 4.0× more often than the national baseline.
1995Peak 20242025
Peak year
2024
Decline from peak
10.9%
2025
595
All-time
4,084
Diaspora map
Cillian spread fast — broke out in Alaska, Colorado, Connecticut, Maine, Maryland, Massachusetts, New York, and Pennsylvania (2024) and ran high in 8 states within a decade.
Broke out: Alaska, Colorado, Connecticut, Maine, Maryland, Massachusetts, New York, and Pennsylvania, 2024 · over-represented in 8 states over 0 years
