| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 361 | Malvyn | Celtic | Leader. | M | |
| 362 | Mariner | Celtic | Lives by the sea. | M | |
| 363 | Marvin | Celtic | Lives by the sea. | M | |
| 364 | Marvyn | Celtic | Lives by the sea. | M | |
| 365 | Medredydd | Celtic | Mythical son of Medredydd. | M | |
| 366 | Melville | Celtic | Leader. | M | |
| 367 | Melvin | Celtic | Leader. | M | |
| 368 | Melvyn | Celtic | Leader. | M | |
| 369 | Menw | Celtic | Mythical a wizard. | M | |
| 370 | Merlin | Celtic | From the hill over the sea. | M | |
| 371 | Merlyn | Celtic | From the hill over the sea. | M | |
| 372 | Morfran | Celtic | Mythical ugly demon. | M | |
| 373 | Morgan | Celtic | Lives by the sea. | M | |
| 374 | Morven | Celtic | Lives by the sea. | M | |
| 375 | Morvyn | Celtic | Lives by the sea. | M | |
| 376 | Moryn | Celtic | Lives by the sea. | M | |
| 377 | Mungo | Celtic | Lovable. | M | |
| 378 | Murdoc | Celtic | Seaman. | M | |
| 379 | Murdoch | Celtic | Seaman. | M | |
| 380 | Murdock | Celtic | Seaman. | M | |