The name is derived from a chief in the 13th century, Sir Laumon, whose charter granting lands to the Paisley Abby, is still in existence.
Few clans can document their existence at such an early date.
Although the name comes from the 13th century chief, the clan is much older, being known as MacKerracher before Sir Laumon's time. Sir Laumon's mother is believed to have been a daughter of the great Somerled, ancestor of the MacDonalds. He took the name of Lyon from the Lamont arms, and chose as his arms, the reverse of the Lamonts, a blue lion on a silver field. In the early 1300s, came a great down turn in the Clan's fortunes. Laumon's grandson, Sir John, supported the MacDougalls of Lorne against Robert the Bruce.