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| Name | Total | Name | Total | Name | Total | Name | Total | Name | Total |
|---|---|---|---|---|---|---|---|---|---|
| Obertacz | 4 | Olafsson | 1 | Oldenburg XVI | 1 | Orkney | 3 | Ostacsdatter | 1 |
| Obotrites | 1 | Olcott | 1 | Olga | 1 | Orr | 1 | Ostfriesland | 2 |
| Odinsson | 1 | Oldenberg | 1 | Oliver | 2 | Orth | 1 | Owen | 25 |
| Oehlmajer | 3 | Oldenburg | 11 | Ollive | 1 | Osborn | 1 | Oxenbridge | 1 |
| Oehlmann | 1 | Oldenburg I | 4 | Ollyver | 1 | Osborne | 3 | Oyly | 1 |
| Oelmaier | 3 | Oldenburg II | 2 | Olmstead (Almstead) | 1 | Osburn | 1 | oyly, D' | 2 |
| Offley | 1 | Oldenburg III | 2 | Onassis | 1 | Osdola, de | 1 | - | - |
| Ogden | 1 | Oldenburg IV | 3 | Orange | 11 | Osgood | 14 | - | - |
| Olaf | 1 | Oldenburg V | 3 | Ordway | 4 | Ossory | 1 | - | - |
| Olafsdottir | 2 | Oldenburg X | 1 | Organ | 1 | Ossory, Of | 2 | - | - |