Starting with letter O
| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 21 | Obiareus | Greek | A Titan. | M | |
| 22 | Obil | Biblical | That weeps, who deserves to be bewailed. | M | |
| 23 | Oboth | Biblical | 'Dragons, fathers, desires' | M | |
| 24 | Oceanus | Greek | Father of the Oceanids. | M | |
| 25 | Ocelfa | English | From the high plain. | M | |
| 26 | Ocnus | Greek | Incompetent. | M | |
| 27 | Ocran | Biblical | A disturber, that disorders. | M | |
| 28 | Octave | French | Born eighth. | M | |
| 29 | Octavian | Latin | Variant of Octavius: Born eighth. Octavian was the name used commonly for the Emperor Augustus. | M | |
| 30 | Octavio | Latin | Eighth. | M | |
| 31 | Octavius | Latin | Born eighth. Octavius was a Roman clan name, as well as the original name of Emperor Augustus (commonly known as Octavian). Traditionally, this name was given to the eighth child in a large family. | M | |
| 32 | Octavius | Shakespearean | Antony and Cleopatra'. Octavius Caesar, Roman triumvir. 'The Tragedy of Julius Caesar' Triumvir after Caesar's death, later Augustus Caesar, first emperor of Rome. | M | |
| 33 | Octe | Anglo-Saxon | A son of Hengist. | M | |
| 34 | Octha | Anglo-Saxon | A son of Hengist. | M | |
| 35 | Octha | ArthurianLegend | Enemy of Arthur. | M | |
| 36 | Ocumwhowurst | NativeAmerican | Yellow wolf (Cheyenne). | M | |
| 37 | Ocunnowhurst | NativeAmerican | Yellow wolf (Cheyenne). | M | |
| 38 | Ocvran | ArthurianLegend | Father of Guinevere. | M | |
| 39 | Odakota | NativeAmerican | Friend (Sioux). | M | |
| 40 | Odale | English | Of the valley. | M | |