Few Scots families can have occupied such varied and widely separated areas of the country than the nomadic Macmillans. There are many theories on their origin but the most popular view is that they are descended from the Siol O'Cain, an ancient Pictish tribe of Moray. The name Macmillan is ecclesiastical in origin, Mac Gillem-haoil "Son of the Tonsured servant", and commemorates descent from an old family of Celtic abbots. An Gillemaol, the Tonsured servant in question was living around 1132 near Elgin where he was listed as witness in the Book of Dear, the oldest Scots religious record. It is believed the Macmillans were transplanted from Loch Arkaig to Crown lands on Lawers near Loch Tay by Malcolm IV around 1160. There they remained for two centuries until once again they were driven from their home and the clan scattered to many regions of Scotland. The main branch to Knapdale, others to Lochaber (many of this line emigrated to Canada during the 19th century), another branch to Galloway spreading later throughout Aryshire and Dumfriesshire and some to the Western Isles; Harold Macmillan, Prime Minister from 1957 to 1963, was descended from the Arran branch. Malcolm Mor Macmillan received Knapdale from the Lord of the Isles in 1360. The charter is said to have been inscribed on a rock. (This was later destroyed by Campbell of Calder in 1615). As vassals of the Lord of the Isles, the Macmillans were caught up in the aftermath of the forfeiture of the Lordship and lost control of Knap forever. They did however manage to keep the adjoining lands of Tireleacham. Even so they were still harassed by the Campbells who had supplanted them. Macmillan of Knap was considered chief of the clan and when the line became extinct in 1665, the title passed to the Dunmore branch, and from them to the Lagalgarve branch in which it is still vested.