First found in Angus, where they were descended from the Gailic MacDhai, son of David. From the 13th century onward the name was anglicized MacDavid, Davidson, Deasson and Deas. The branches using Deas and Deasson settled in Angus and in Banffshire at the end of the fifteenth century.

The cruelties suffered under the new government forced many to leave their ancient homeland for the freedom of the North American colonies. Those who arrived safely found land, freedom, and opportunity for the taking. These hardy settlers gave their strength and perseverance to the young nations that would become the United States and Canada. Immigration and passenger lists have shown many early immigrants bearing the name Deas: Dennis Dease, who settled in Philadelphia Pa. in 1855; another Dennis, who settled there in 1863; Patrick Deasey, who settled in Philadelphia in 1835.

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