| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 441 | Cianan | Irish | Variant of Cian: Old; ancient; archaic. | M | |
| 442 | Ciar | Irish | Saint. | F | |
| 443 | Ciara | Irish | Saint or Dark. Feminine of Ciaran. | F | |
| 444 | Ciaran | Irish | Black-haired. | M | |
| 445 | Ciardha | Irish | Variant of Ciaran: Black-haired. | M | |
| 446 | Ciarrai | Irish | County. Variant of Ciaran: Black-haired. | M | |
| 447 | Ciatlllait | Irish | Archaic. | F | |
| 448 | Cillan | Irish | Variant of Ceallach: War; strife. | M | |
| 449 | Cillian | Irish | Variant of Ceallach: War; strife. | M | |
| 450 | Cinneide | Irish | Variant of Cinneidid: Helmeted; helmed head. | M | |
| 451 | Cinneidid | Irish | Helmet head; helmed head. | M | |
| 452 | Cinneidigh | Irish | Variant of Cinneidid: Helmeted; helmed head. | M | |
| 453 | Clancey | Irish | Variant of Clancy: The red-haired soldier's son; ruddy warrior. | M | |
| 454 | Clancy | Irish | The red-haired soldier's son; ruddy warrior. | M | |
| 455 | Cleary | Irish | Educated. | M | |
| 456 | Cleonie | Irish | From the Greek Cleone: daughter of a river god. | F | |
| 457 | Clodagh | Irish | From the name of an Irish river, Clodagh is used occasionally as a first name in Ireland. | F | |
| 458 | Cluny | Irish | From the meadow. | M | |
| 459 | Coachuhhar | Irish | High desire. | M | |
| 460 | Cochlain | Irish | Hooded. | M | |