First found in County Clare, where they were seated from very ancient times. They were descended from O'Dea who in turn was descended from the Heremon Kings.

In the 18th and 19th centuries, thousands of Irish Families fled an Ireland that was forcibly held through by England through its imperialistic policies. A large portion of these families crossed the Atlantic to the shores of North America. The fate of these families depended on when they immigrated and the political allegiances they showed after they arrived. Settlers that arrived before the American War of Independence may have moved north to Canada at the war's conclusion as United Empire Loyalists. Such Loyalists were granted land along the St. Lawrence River and the Niagara Peninsula. Those that fought for the revolution occasionally gained the land that the fleeing Loyalist vacated. After this period, free land and an agrarian lifestyle were not so easy to come by in the East. So when seemingly innumerable Irish immigrants arrived during the Great Potato Famine of the late 1840s, free land for all was out of the question. These settlers were instead put to work building railroads, coal mines, bridges, and canals. Whenever they came, Irish settlers made an inestimable contribution to the building of the New World. Early North American immigration records have revealed a number of people bearing the Irish name O'Day or a variant listed above, including: Stephen Day who became a prominent merchant in Virginia soon after arriving in 1638. Another Stephen Daye (1594-1668), was the first printer in New England, and produced the first book printed in the English colonies. Cambridge Massachusetts granted his three hundred acres of land for "being the first that sett upon printing." A large contingent of the family also settled in Canada beginning in the 1840's..

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