| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 641 | Lynnette | Welsh | Variant of ancient Welsh given name Eluned: From 'cilun' meaning idol. In Arthurian legend Lynette accompanied Sir Gareth on a knightly quest. | F | |
| 642 | Mabli | Welsh | Welsh form of Mabel, meaning lovable. | F | |
| 643 | Mabon | Welsh | Legendary son of Modron. | M | |
| 644 | Mabsant | Welsh | Legendary son of Caw. | M | |
| 645 | Madawc | Welsh | Beneficent. | M | |
| 646 | Madawg | Welsh | Legendary son of Teithyon. | M | |
| 647 | Maddoc | Welsh | Beneficent. | M | |
| 648 | Maddock | Welsh | Beneficent. | M | |
| 649 | Maddockson | Welsh | Son of Maddock. | M | |
| 650 | Maddocson | Welsh | Son of Maddock. | M | |
| 651 | Maddog | Welsh | Beneficent. | M | |
| 652 | Maddox | Welsh | Son of Maddock. | M | |
| 653 | Madoc | Welsh | Fortunate. Beneficent. | M | |
| 654 | Madog | Welsh | Beneficent. | M | |
| 655 | Maegan | Welsh | Variant of Margaret - pearl - based on the abbreviation Meg. | F | |
| 656 | Mael | Welsh | Legendary son of Roycol. | M | |
| 657 | Maelgwyn | Welsh | Prince of the hounds. | M | |
| 658 | Maelwys | Welsh | Legendary son of Baeddan. | M | |
| 659 | Mair | Welsh | Bitter. | F | |
| 660 | Mali | Welsh | Welsh form of Molly: bitter. | F | |