The name is Gaelic in origin, deriving from "MacGille Fhaolain""son of the servant of St. Filan". St. Filan was a missionary of the old Celtic church, and there is a village in Perthshire named after him. The name Filan itself is derived from the Celtic "faelchu", meaning "wolf". The Maclellans were numerous in Galloway and gave their name to Balmaclellan in Stewartry. Duncan Mac Lellan appears in a charter of Alexander II in 1217. Mac Lellan of Bombie was among the close followers of Sir William Wallace when he left Kirkcudbright for France after the defeat at Falkirk in 1293. In the early fifteenth century it is said there were no fewer than fourteen knights of the name Mac Lellan in Galloway. Sir Patrick Mac Lellan of Bombie forfeited his lands for marauding through the lands of the Douglases, the Lords of Galloway. James II restored the lands when Sir Patrick' s son, Sir William, captured the leader of a band of gypsies who were terrorising the district and carried the head of the brigand to the king on the point of his sword. This is one explanation advanced for the origins of the crest of this family, although moors' heads are often considered to be an allusion to the Crusades. In 1452, eighth Earl of Douglas, captured Sir Patrick Mac Lellan and held him in Threave Castle for refusing to join a conspiracy against the king. Sir Patrick' s uncle, who held high royal office, obtained letters ordering the release of Douglas' s prisoner but when Douglas was presented with the royal warrant he promptly had Sir Patrick murdered.
Sir William Mac Lellan of Bombie was knighted by James IV. He followed his king on the ill-fated invasion of England which ended at Flodden field in 1513. His great-grandson, Sir Robert, was a courtier both to James IV and Charles I, and in 1633 was raised to the peerage as Lord Kirkcudbright. The third Lord incurred enormous debts for the king' s cause during the civil war and completely ruined the estates. The title passed from cousin to brother to cousin, with very few direct male heirs, At the beginning of the eighteenth century there were two claimants to the title. The dispute was finally settled by the House of Lords in 1761 but the title again became dormant in 1832 when the ninth Lord died in Bruges.