Although the name is without doubt among the oldest in Scotland–-a MacInnes is said to have lived on Iona with Saint Columba in the 6th Century–-it is remarkable how little is known of this clan's history.
The name McInnis is derived from the Celtic "MacAonghais," meaning son of Angus. McInnis is just one of many phonetic attempts at spelling the Angicized form of the name. Others are MacInnes, McGinnis, MacInnish, McKynes, and even M'Aneiss. The Mc spelling is a shorthand version of Mac, and in years past was written with a short line, called a macron, over the c to indicate the abbreviation. In some quarters, the short line became two short lines, and they were placed under the c.
The MacInnes clan were some of the original Scottish inhabitants of Morvern, a peninsula on the western shore of northern Scotland. This is part of the region known as Argyll, meaning "coastland of the Gael." Gaelic-speaking people first appeared there in the 6th century AD when Dalriadic Scots settlers arrived from County Antrim, Ireland. The Kingdom of Dalriada was under the direction of three brothers, Lorn, Fergus and Angus. Soon they divided the kingdom into three tribes: Ceantir was the portion of Fergus, Lorn possessed Lorn, and Angus colonized Isla. Subsequently many more Gaelic speaking settlers arrived to overwhelm the indigenous Pictish peoples and the entire area became known as Scotland
By the time of Somerled, who was the first Lord of the Isles, McInnis folks were well established in Morvern. A popular McInnis story tells how they became vassals to the Lords of the Isles. Once when the Vikings were terrorizing their neighborhood, the Chiefs of McInnis went to the great warrior Somerled to get advice. Somerled agreed to help them if they would follow his directions exactly. Faced with defeat, the McInnis Clan, who would never take advice otherwise, agreed to his terms. He told them to march in their kilts in full view of the Vikings. Then he advised them to kill a herd of highland cattle, and parade in front of the Vikings covered in the cowhides with the long, shaggy fur on the outside. Then he told them to parade a third time, with the smooth side of the skins turned outward. The Vikings were fooled, as Somerled predicted, into thinking the McInnis Clan had three times its fighting strength. They fled in the face of overwhelming numbers. In thanks to Somerled for his help, McInnis vowed to become his vassal.
The McInnis Clan of Morvern prospered for awhile. They were called the keepers of Kinlochaline Castle. This fortress is known as Caiteal an Im (Castle of Butter). The Lady of Clan McInnis, Dubh Chal was said to have paid the builder with butter to the capacity of the castle. ( It is not clear if "keeper" means owner.)The last McInnis chief along with his sons was killed while they were guests of the MacLeans at Ardtornish Castle under the orders of John MacDonald, Lord of the Isles. The McInnis leadership had managed to run afoul of the powerful MacDonalds and were ruined forever.