| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 401 | Cathasach | Irish | Brave. | F | |
| 402 | Catherine | Irish | Variant of Katherine: Pure. Clear. Innocent. From the Gaelic form Caitlin. | F | |
| 403 | Cathleen | Irish | Variant of Katherine: Pure. Clear. Innocent. From the Gaelic form Caitlin. | F | |
| 404 | Cathmor | Irish | Great fighter. | M | |
| 405 | Cathmore | Irish | Great fighter. | M | |
| 406 | Cathryn | Irish | Form of the Greek Catherine meaning 'pure'. | F | |
| 407 | Cathy | Irish | Diminutive of Katherine: Pure. Clear. From the Gaelic form Caitlin. | F | |
| 408 | Catlee | Irish | Pure. | F | |
| 409 | Catlin | Irish | Variant of Katherine meaning pure. | F | |
| 410 | Catline | Irish | Variant of Katherine meaning pure. | F | |
| 411 | Catlyn | Irish | Variant of Katherine meaning pure. | F | |
| 412 | Catriona | Irish | Variant of Katherine meaning pure. | F | |
| 413 | Cattee | Irish | Variant of Katherine meaning pure. | F | |
| 414 | Caulan | Irish | Variant of Caelan: Powerful warrior. | M | |
| 415 | Cavan | Irish | Good-looking; handsome; from Cavan. | M | |
| 416 | Cavana | Irish | From Cavan. | F | |
| 417 | Cayce | Irish | Variant of Casey: Observant; alert; vigorous. | M | |
| 418 | Caycee | Irish | Vigilant. | F | |
| 419 | Caycey | Irish | Variant of Casey: Observant; alert; vigorous. | M | |
| 420 | Ceallach | Irish | War; strife. | M | |