| NAME | MEANING |
| OBA | Name of ancient river goddess |
| OBELIA | Needle |
| OCEAN | Ocean |
| OCTAVIA | Eighth |
| ODEDA | Strong |
| ODELETTE | Little song |
| ODELIA | I will praise God |
| ODELLA | Wood hill |
| ODELYN | Wood hill |
| ODERA | Plough |
| ODESSA | meaning unknown |
| ODETTE | Possessions |
| ODILE | Possessions |
| OFIRA | Gold |
| OGIN | Wild rose |
| OKALANI | Of the heavens |
| OKI | In middle of the ocean |
| OLA | Defender of men |
| OLATHE | Beautiful |
| OLEDA | Noble |
| OLEKSA | Defender of men |
| OLENA | Bright one |
| OLENKO | Bright one |
| OLÉSIA | Defender of men |
| OLÉSYA | Defender of men |
| OLETA | Noble |
| OLGA | Holy |
| OLIA | Holy |
| OLIANA | Oleander |
| OLIFF | Name of a fruit |
| OLINA | Name of a fruit |
| OLINDA | A greek city |
| OLISA | God |
| OLIVA | Name of a fruit |
| OLIVE | Name of a fruit |
| OLIVETTE | Name of a fruit |
| OLIVIA | meaning unknown |
| OLKA | Holy |
| OLLI | Holy |
| OLLIE | Name of a fruit |
| OLUNKA | Holy |
| OLUSKA | Holy |
| OLVA | Holy |
| OLWEN | Footprint |
| OLYA | Holy |
| OLYUSHA | Holy |
| OMA | Eloquent |
| OMEGA | meaning unknown |
| OMUSA | To miss a deer with arrows |
| ONA | Grace |
| ONATAH | Corn spirit |
| ONAWA | Wide-awake one |
| ONELLA | Bright one |
| ONI | Born on holy |
| ONIDA | Looked for one |
| ONITA | meaning unknown |
| OONA | Remember |
| OONAGH | Remember |
| OONIE | Remember |
| OPAL | Gem |
| OPHELIA | Help |
| OPHIRA | Gold |
| OPRAH | meaning unknown |
| ORAH | Light |
| ORALEE | My light |
| ORALIA | Dawn |
| ORANGE | Orange tree |
| ORANGETTA | Orange tree |
| ORELDA | Dawn |
| ORELLE | Dawn |
| ORENDA | Magic powers |
| ORI | Weavers |
| ORIANA | Dawn |
| ORIEL | Golden |
| ORINA | Peace |
| ORINDA | Mountain |
| ORINO | Weavers |
| ORINTHIA | Mountain |
| ORIOLE | Golden |
| ORIT | Light |
| ORLA | Golden lady |
| ORLAGH | Golden lady |
| ORLANN | Dawn |
| ORLENDA | Female eagle |
| ORLENE | Dawn |
| ORLI | My light |
| ORLICE | My light |
| ORNA | Fir tree |
| ORNICE | Fir tree |
| ORNIT | Fir tree |
| ORPAH | meaning unknown |
| ORPHA | meaning unknown |
| ORPHY | meaning unknown |
| ORSA | Little she-bear |
| ORSEL | Little she-bear |
| ORSOLA | Little she-bear |
| ORYA | Peace |
| ORYNA | Peace |
| OSEN | Thousand |
| OSYTH | meaning unknown |
| OUIDA | Famous warrior |
| OWENA | Well-born |
| OYA | To name |