| Kieran | Cillian | |
|---|---|---|
| Meaning | little dark one | Bright-headed; church |
| Origin | irish | Irish |
| Gender | Boy | Boy |
| Pronunciation | KEER-uhn | KIL-ee-un |
| Syllables | 2 | 2 |
| First appeared | 1918 | 1995 |
| Peak year | 2025 (817) | 2024 (668) |
| In 2025 | 817 | 595 |
| Trend | Near its peak | Near its peak |
Source: US Social Security Administration.
| Decade | Kieran | Cillian |
|---|---|---|
| 2020s | 3,946 | 2,662 |
| 2010s | 5,282 | 1,204 |
| 2000s | 4,412 | 208 |
| 1990s | 2,177 | 10 |
| 1980s | 610 | 0 |
| 1970s | 415 | 0 |
| 1960s | 374 | 0 |
| 1950s | 222 | 0 |
| 1940s | 81 | 0 |
| 1930s | 48 | 0 |
| 1920s | 38 | 0 |
| 1910s | 8 | 0 |
Anglicized from Irish Ciaran, a diminutive of 'ciar' meaning 'black, dark', giving 'little dark one'. Borne by several early Irish saints.
Cillian is linked to “bright-headed” and to cill, “church” or “monastery.”
Kieran is more popular than Cillian today: about 817 US babies were given the name Kieran in 2025, compared with 595 named Cillian.
Kieran means little dark one (irish origin), while Cillian means Bright-headed; church (Irish origin).
In US records, Kieran first appears in 1918 and Cillian in 1995, so Kieran has the longer recorded history.