There is lots of data on the Madill family at this site. Marilyn Evans has great information on Ontario Madills. There are many variations in the spelling of Madill that you might examine. The name probably came from the French word for metal worker.It is likely that your branch of the family entered Ireland from Holland with the army of William of Orange.The Madill in my family came from a farm in Co. Monaghan near the border with Co. Cavan, just south of Drum. There are many Madills listed in Griffith's Valuation for that area.