| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 601 | Cruadhlaoich | Irish | Hunch backed. | M | |
| 602 | Cuanaic | Irish | Handsome. | M | |
| 603 | Cuilean | Irish | Variant of Coilean: Puppy. | M | |
| 604 | Cuinn | Irish | Wise; intelligent. | M | |
| 605 | Cullan | Irish | Good-looking lad. Also a variant of Cullent: Holly. | M | |
| 606 | Cullen | Irish | Good-looking lad. Surname. | M | |
| 607 | Cullent | Irish | Holly. | M | |
| 608 | Cullin | Irish | Good-looking lad. Also a variant of Cullent: Holly. | M | |
| 609 | Cullo | Irish | Hound of Ulster. | M | |
| 610 | Cully | Irish | Diminutive of Cullent: Holly. | M | |
| 611 | Cumania | Irish | Name of a saint. | F | |
| 612 | Cumhea | Irish | Hound of the plains. | M | |
| 613 | Curran | Irish | Hero. | M | |
| 614 | CuUladh | Irish | Hound of Ulster. | M | |
| 615 | Cuyler | Irish | Chapel. | M | |
| 616 | D'arcy | Irish | Dark. | F | |
| 617 | Daeg | Irish | Black-haired. | M | |
| 618 | Daegan | Irish | Black-haired. | M | |
| 619 | Dagen | Irish | Black-haired. | M | |
| 620 | Dahy | Irish | Capable; quick and agile. | M | |