| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 421 | Quin | Celtic | Wise. | M | |
| 422 | Quinn | Celtic | Wise. | M | |
| 423 | Reagan | Celtic | Regal. | M | |
| 424 | Reaghan | Celtic | Regal. | M | |
| 425 | Regan | Celtic | Regal. | M | |
| 426 | Reghan | Celtic | Regal. | M | |
| 427 | Ronan | Celtic | Oath. | M | |
| 428 | Roy | Celtic | Red haired. | M | |
| 429 | Sativola | Celtic | Name of a saint. | M | |
| 430 | Sawyer | Celtic | Cuts timber. | M | |
| 431 | SciIti | Celtic | Legendary messenger of Arthur. | M | |
| 432 | Setanta | Celtic | Mythical son of Sualtam. | M | |
| 433 | Sheridan | Celtic | Untamed. | M | |
| 434 | Sloan | Celtic | Fighter. | M | |
| 435 | Sloane | Celtic | Fighter. | M | |
| 436 | Sugn | Celtic | Mythical son of Sugnedudd. | M | |
| 437 | Tadhg | Celtic | Mythical a prince of Munster. | M | |
| 438 | Taliesin | Celtic | Bard. | M | |
| 439 | Tanguy | Celtic | Fighter. | M | |
| 440 | Teaghue | Celtic | Bard. | M | |