Last name O'Halloran (O'Halloran 
) , worldwide, is quite a common surname. The surname O'Halloran is characteristic of Ireland, where it is quite a common surname, Australia, where it is quite a rare surname, and New Zealand. In absolute terms, it is the most numerous in Australia, Ireland, and the United States.
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| O'Halloran | United Kingdom, Australia, Ireland, United States, Canada |
| sylvester o'halloran Irish surgeon (b. 1728) |
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thomas shuldham o'halloran Australian politician (1797-1870), IO (b. 1797) |
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| joseph o'halloran Irish soldier (b. 1763) |
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| charles sylvester o'halloran (1791-1812) (b. 1791) |
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joseph o'halloran Secretary of the Royal Colonial Institute, AU (b. 1842) |
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| frances bayly o'halloran (born 1793) (b. 1793) |
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| ann helen o'halloran (1795-1856) (b. 1795) |
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| st. george o'halloran (1799-1815) (b. 1799) |
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| henry dunn o'halloran (1800-1871) (b. 1800) |
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| edward paget o'halloran (1802-1831) (b. 1802) |
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| sophia sherbourne o'halloran (1803-1832) (b. 1803) |
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| william adlam o'halloran plantation owner in Jamaica, 1804 - 1846 (b. 1804) |
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| william littlejohn o'halloran British Army officer and public servant in South Australia (b. 1806) |
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| frances bayly o'halloran (born 1807) (b. 1807) |
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| joseph palmer o'halloran (1807-1825) (b. 1807) |
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