| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 421 | Omolf | Norse | Son of Armod. | M | |
| 422 | Onund | Norse | Son of Viking. | M | |
| 423 | OrIyg | Norse | Son of Valthjof. | M | |
| 424 | Orm | Norse | Son of Ulf. | M | |
| 425 | Os | Norse | Divine. | M | |
| 426 | Osborn | Norse | Divine bear. | M | |
| 427 | Osborne | Norse | Variant of Osborn: Divine bear. | M | |
| 428 | Oscar | Norse | Divine spear. | M | |
| 429 | Osgood | Norse | A divine Goth. | M | |
| 430 | Oskar | Norse | Divine spear. | M | |
| 431 | Ospak | Norse | Brother of Gudrun. | M | |
| 432 | Ostein | Norse | Happy. | M | |
| 433 | Osten | Norse | Happy. | M | |
| 434 | Osvif | Norse | Father of Gudrun. | M | |
| 435 | Othin | Norse | God of the sky. | M | |
| 436 | Ottar | Norse | Fighter. | M | |
| 437 | Ovaegir | Norse | Father of the Skraeling children. | M | |
| 438 | Ove | Norse | Ancestors. | M | |
| 439 | Oysten | Norse | Happy. | M | |
| 440 | Ozur | Norse | Son of Thorleif. | M | |