Cognomen O'Day (O'Day 
, אודיי 
) , in the world, is quite a rare last name. The family name O'Day is characteristic of Australia, where it is a rare surname, the United States, and New Zealand. Measured by absolute frequency, it most frequently occurs in the United States, Australia, and Japan. Very seldom, O'Day is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| O'Day | United Kingdom, Japan, Canada, Australia, United States |
| אודיי | Israel |
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hank o'day American baseball player, manager, umpire, US (b. 1859) |
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daniel o'day (1870-1916) American businessman, US (b. 1870) |
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peggy o'day actor (1900-1964), US (b. 1900) |
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| john o'day American politician, US (b. 1856) |
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nell o'day actress (1909-1989), US (b. 1909) |
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molly o'day American film actress (1911-1998), US (b. 1911) |
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anita o'day American jazz singer (1919–2006), US (b. 1919) |
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| tommy o'day Australian rules footballer, AU (b. 1873) |
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| alice o'day Irish actress, IE (b. 1882) |
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alan o'day American singer-songwriter, US (b. 1940) |
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| marcus o'day American physicist, US (b. 1897) |
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james o'day politician in Massachusetts, US, US (b. 1954) |
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| molly o'day Singer, musician (1923-1987), US (b. 1923) |
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| george o'day sailor, US (b. 1923) |
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jeremy o'day Canadian football player, US (b. 1974) |
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