I just came across your January question about McCoy and Mackay. My McCoy was originally Mackay. When my Mackay ancestors arrived in Canada in 1750s they signed their names "Mackay". They married French Canadian women and remained in Canada after the end of the war. The name remained Mackay until mid 1800s when one of my ancestors began going by McKay. About 1880 his son moved to Michigan and becameknown as McCoy. It is my understanding that McCoy is usually an Irish name.