| Orvar | An old Norse name meaning arrow war. |
| Orvo | A Finnish word for 'winter' |
| Osippa | God will Add Another Son |
| Oski | Divine Spear; Gentle Friend |
| Osku | Divine Spear, Gentle Friend |
| Osmo | A Finnish name meaning a brave man. |
| Osmu | A variant form of the name Osmo. |
| Oso | A Spanish name meaning a bear. |
| Osse | A short form of the name Osvald. |
| Ossee | A variant of the name Hosea. |
| Ossiaan | Derived from a Gaelic hero. |
| Osva | A name meaning divine spear. |
| Osvaltti | Possibly Divine Power |
| Osvi | Possibly Divine Power |
| Oti | A name meaning wealthy one. |
| Otsa | A name meaning a forehead. |
| Otso | A name meaning a male bear. |
| Otu | Collecting Seashells in a Basket |
| Otukka | A name meaning a small bug. |
| Paanus | From the City; City Dweller |
| Paaso | A name meaning a mountain. |
| Paatsa | A name meaning a bird cherry. |
| Paatsi | A name meaning a bird cherry. |
| Paaval | A Finnish form of the name Paul. |
| Paavali | The Finnish version of the name Paul. |
| Paavi | The Finnish word for the Pope. |
| Paavoo | A variant spelling of the name Paavo. |
| Pake | A name meaning a person from Hawaii. |
| Patrikki | A Patrician; A Noble Mane |
| Patro | A name derived from the word patron. |
| Patu | A Finnish term for a small creature. |
| Paukka | A surname of Finnish origin meaning bang. |
| Paukku | A Finnish word meaning a loud pop. |
| Paulja | A rare variant of the name Paulina. |
| Paunus | A name of Finnish origin meaning small. |
| Pavelko | A Slavic name meaning little Paul. |
| Peenhartti | Brave like a Bear |
| Peetu | Loving; Kindness; Charity |
| Peivas | A name meaning the sun or daylight. |
| Pekko | A Finnish name meaning rock or stone. |