Septs of Clan MacMillan: Baxter, Bell, Blue, Brown, Calman, Leny, Mcolmin, Mildonich, Mnucator, Melanson, Millan, Walker.
The MacMillans are one of the oldest clans in Scotland, being descended from a 12th century monk or lay priest called Gilchrist; a son of Cormac bishop of Dunkeld, whose great-great-grandfather was the Scots king Macbeth. The collective name of his descendants, the Clann an Mhaoil or "Children of the Tonsured One" comes from the Gaelic nickname that Gilchrist bore:
Maolan, “The (little) Tonsured One”
or An Gillemaol, “The Tonsured Servant (of God)”
The two resulting surnames, MacMhaolain and MacGhillemhaoil, have been transcribed phonetically by Scots and English speaking people in over 180 different ways over the centuries; so there is no "correct" English version, though the majority of modern clan members use variations on the three most usual forms: Macmillan, MacMillan, McMillan.
George MacMillan, the current Clan Chief, is the twenty third generation after Gilchrist Maolan, and the 12xGreat-Grandson of Alexander MacMillan of Knap, the 15th century Constable of Castle Sween and erector of the famous Celtic Cross at Kilmory Knap.
For more information about Clan MacMillan, visit the Clan Centre's own web-site at: http://www.clanmacmillan.org