Starting with letter O
| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 1 | O' | Irish | Descendent of. Irish surnames formed by prefacing O'. | M | |
| 2 | O'brian | Irish | Surname. | M | |
| 3 | O'brien | Irish | Surname. | M | |
| 4 | O'keefe | Irish | Surname. | M | |
| 5 | O'shay | Irish | Surname. | M | |
| 6 | O'shea | Irish | Surname. | M | |
| 7 | Oakden | English | From the oak tree valley. | M | |
| 8 | Oakes | English | From the oak. | M | |
| 9 | Oakley | English | From the oak - tree meadow. | M | |
| 10 | Oates | German | Variant of Odo: Wealth. | M | |
| 11 | Oba | Egyptian | King. | M | |
| 12 | Obadiah | Biblical | Servant of the Lord | M | |
| 13 | Obadiah | Hebrew | Servant/worshipper of the Lord. Obadiah was the prophet who wrote the shortest book in the Old Testament. | M | |
| 14 | Obal | Biblical | Inconvenience of old age. | M | |
| 15 | Obed | Biblical | A servant; workman | M | |
| 16 | Obed-edom | Biblical | Servant of Edom | M | |
| 17 | Obediah | Hebrew | Serves God. | M | |
| 18 | Oberon | English | In A Midsummer Night's Dream, Shakespeare altered the spelling to Auberon, king of the fairies, to Oberon. | M | |
| 19 | Oberon | German | Noble and bear-like. In a Midsummer Night's Dream, Shakespeare altered the spelling of Auberon (King of the fairies) to Oberon. | M | |
| 20 | Oberon | Shakespearean | A Midsummer Night's Dream' King of the Fairies. | M | |