| Firstname | Gender | Origin | Meaning of name | Form | Pronunciation |
|---|---|---|---|---|---|
| Oakley |  | English | From the oak meadow | Itself | (OAK lee) |
| Obadiah | | Hebrew | God's worker | (o ba DIE a) | |
| Obadias | | Hebrew | God's worker | (o ba DIE us) | |
| Obed | | Hebrew | Servant, worshipper | Itself | (O bed) |
| Obediah | | Hebrew | God's worker | (o ba DIE a) | |
| Oberon | | German | Noble bear | Auberon | (OH ber on) |
| Ocean | | Greek | Ocean | (O shun) | |
| Octavian | | Latin | Eighth | (AHK tay vee ahn) | |
| Octavius | | Latin | Eighth | Itself | (ahk TAY vee us) |
| Odell | | English | Woad hill | Itself | (o DEL) |
| Firstname | Gender | Origin | Meaning | Form | Pronunciation |
|---|---|---|---|---|---|
| Odie | | English | Woad hill | Odell | (O dee) |
| Odin | | Norse | Inspiration, frenzy | Itself | (O din) |
| Odysseus | | Greek | Full of wrath | Itself | (oh DIH see us) |
| Ogdan | | English | Oak valley | Ogden | (AWG den) |
| Ogden | | English | Oak valley | Itself | (AWG den) |
| Ogdon | | English | Oak valley | Ogden | (AWG den) |
| OisÃn | | Gaelic | Little deer | Itself | (osh EEN) |
| Olaf | | Norse | Ancestor | Itself | (O lahf) |
| Olander | | Swedish | From the island of Oland | Itself | (O lan der) |
| Ole | | Norse | Ancestor | Olaf | N/A |