| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 1301 | Lil | Irish | Name of a saint. | F | |
| 1302 | Lochlain | Irish | Home of the Norse. | M | |
| 1303 | Lochlann | Irish | Home of the Norse. | M | |
| 1304 | Loman | Irish | Bare. | M | |
| 1305 | Lorcan | Irish | Little fierce one. | M | |
| 1306 | Loughlin | Irish | Servant. | M | |
| 1307 | Lugaidh | Irish | Famous warrior. | M | |
| 1308 | Luighseach | Irish | Torch bringer. | F | |
| 1309 | Lun | Irish | Strong. | M | |
| 1310 | Lunn | Irish | Strong. | M | |
| 1311 | Lyam | Irish | Form of William. | M | |
| 1312 | Mab | Irish | Happiness. | F | |
| 1313 | Mabbina | Irish | Happiness. | F | |
| 1314 | Macartan | Irish | Son of Artan. | M | |
| 1315 | MacAuliffe | Irish | Son of Olaf. | M | |
| 1316 | MacBride | Irish | Son of Bridget 'Bride'. | M | |
| 1317 | MacCormack | Irish | Son of Cormac. | M | |
| 1318 | MacElroy | Irish | Son of Elroy. | M | |
| 1319 | Macha | Irish | Plain. | F | |
| 1320 | MacMaureadhaigh | Irish | Son of Murray. | M | |