| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 241 | Caycey | Irish | Variant of Casey: Observant; alert; vigorous. | M | |
| 242 | Ceallach | Irish | War; strife. | M | |
| 243 | Ceallachan | Irish | Variant of Ceallach: War; strife. | M | |
| 244 | Cearbhall | Irish | Manly. | M | |
| 245 | Cearnach | Irish | Victorious. | M | |
| 246 | Cein | Irish | Archaic. | M | |
| 247 | Celsus | Irish | Name of a saint. | M | |
| 248 | Chann | Irish | Young wolf. | M | |
| 249 | Channe | Irish | Young wolf. | M | |
| 250 | Channing | Irish | Young wolf. | M | |
| 251 | Channon | Irish | Young wolf. | M | |
| 252 | Cian | Irish | Old; ancient; archaic. | M | |
| 253 | Cianan | Irish | Variant of Cian: Old; ancient; archaic. | M | |
| 254 | Ciaran | Irish | Black-haired. | M | |
| 255 | Ciardha | Irish | Variant of Ciaran: Black-haired. | M | |
| 256 | Ciarrai | Irish | County. Variant of Ciaran: Black-haired. | M | |
| 257 | Cillan | Irish | Variant of Ceallach: War; strife. | M | |
| 258 | Cillian | Irish | Variant of Ceallach: War; strife. | M | |
| 259 | Cinneide | Irish | Variant of Cinneidid: Helmeted; helmed head. | M | |
| 260 | Cinneidid | Irish | Helmet head; helmed head. | M | |