| Oana | | | Gender: | Female | | Origin: | Romanian |
| | | | | Nickname for Romanian Ioana, meaning "God is gracious". |
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| Oanez | | | Gender: | Female | | Origin: | Breton |
| | | | | Breton form of Agnes, meaning "chaste; holy". |
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| Ocean | | | Gender: | Unisex | | Origin: | English |
| | | | | English unisex name derived from the vocabulary word, itself from Greek Okeanos, meaning "ocean". |
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| Oceane | | | Gender: | Female | | Origin: | French |
| | | | | (Océane) French name derived from the French vocabulary word océan, meaning "ocean". |
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| Octavia | | | Gender: | Female | | Origin: | Roman |
| | | | | Feminine form of Roman Octavius, meaning "eighth". |
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