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| Name | Total | Name | Total | Name | Total | Name | Total | Name | Total |
|---|---|---|---|---|---|---|---|---|---|
| Osborn | 18 | Ogle | 1 | Onstott | 3 | Ossory, of | 1 | Oliver | 7 |
| Owens | 5 | Owen | 1 | Obotrites, the | 1 | Oilly, de | 2 | Oliphent | 1 |
| Owensby | 1 | Okeover | 1 | Olafsdottir | 1 | Orkney, of | 1 | - | - |
| Oldham | 1 | Olive | 1 | Omer, St. | 1 | Oeningen, von | 1 | - | - |
| Orr | 4 | Osbourn | 6 | Other | 1 | Oehler | 7 | - | - |
| Ordeneaux | 1 | Oestritch | 1 | Orléans, de | 1 | Orsby | 1 | - | - |