| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 401 | Odd | Norse | Point. | M | |
| 402 | Oddleif | Norse | Point descendant. | M | |
| 403 | Oddvar | Norse | Pointable. | M | |
| 404 | Odell | Norse | Wealthy. | M | |
| 405 | Odin | Norse | God of the sky. | M | |
| 406 | Oilibhear | Norse | Relic. | M | |
| 407 | Ola | Norse | Relic. | M | |
| 408 | Olaf | Norse | Relic; ancestral heritage. St. Olaf is the patron saint of Norway, and there were many kings in Scandinavia named Olaf. | M | |
| 409 | Olav | Norse | Variant of Olaf: Relic; ancestral heritage. | M | |
| 410 | Olave | Norse | Variant of Olaf: Relic; ancestral heritage. | M | |
| 411 | Ole | Norse | Relic. | M | |
| 412 | Oleif | Norse | Relic descendant. | M | |
| 413 | Olen | Norse | Relic. | M | |
| 414 | Olin | Norse | Relic. | M | |
| 415 | Oliver | Norse | Affectionate. | M | |
| 416 | Olof | Norse | Relic. | M | |
| 417 | Olvaerr | Norse | Affectionate. | M | |
| 418 | Olvir | Norse | Affectionate. | M | |
| 419 | Olyn | Norse | Relic. | M | |
| 420 | Om | Norse | Father of Idunn. | M | |