Some historians attribute this clan to one of the branches of the Siol Alpin, from whom also decend the MacGregors. It has equally been asserted that they stem from Amalghaidh, a younger son of the Earl of Lennox. The name figures in the Ragman Roll in 1296, where it states that Maurice de Arncaple, who submitted to Edward I of England, was the ancestor of the Lairds of Ardincaple, which was to become the principle Macaulay seat. In 1587 Sir Aulay Macaulay of Ardencaple was noted as a principle vassal of the Earl of Lennox and appears to have retained his lands until the late 18th century.

The Macaulays of Lewis were of Norse decent, their name meaning simply, ‘son of Olaf’, by way of the Viking invaders. In the 16th century one of the chiefs of the Lewis Macaulays was known as Donald Camm, meaning Donald One-Eye, who was known for his great strength and quarrelsome nature. His son followed the Marquess of Montrose in his campaign for Charles I during the civil war, and died at the battle of Aldern in 1645.