First found in Connacht, where the Blake family were one of the Tribes of Galway, descending from Richard Caddell (le Blac), sheriff of Connacht in 1303, who came to Ireland with Prince John in 1185, and used both the surnames Caddell and Blake. The name Caddell is Welsh, and means "warlike." It was not replaced completely by Blake until the 17th century, and for three hundred years, people with these surnames were referred to in municipal records by both names. Richard Caddle was sheriff of Connaught in 1306 A.D. and was a tenant of Falway under Richard de Burgo (Burke), the Red Earl of Ulster.

A massive wave of Irish immigrants hit North America during the 19th century. Although many early Irish immigrants made a carefully planned decision to leave left Ireland for the promise of free land, by the 1840s immigrants were fleeing a famine stricken land in desperation. The condition of Ireland during the Great Potato Famine of the late 1840s can be attributed to a rapidly expanding population and English imperial policies. Those Irish Families that arrived in North America were essential to its rapid social, industial, and economic development. Passenger and immigration lists have revealed a number of early Irish immigrants bearing the name O'Blak: William Blake who came from Essex, England, sailed on the "Mary and John" in 1630 and settled in Dorchester, Massachusetts; George Blake settled in Gloucester in 1640.

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