From Wikipedia

Highland Clans

Clan Campbell

Clan Campbell is historically one of the largest, most powerful and most successful of the Highland Scottish clans.

The origins of Clan Campbell are uncertain. The earliest attested Campbell is Gilleasbaig of Menstrie (floruit 1260s), father of Cailean Mór, from whom the chiefs of the clan are thought to have taken their style MacCailean Mór. The byname kambel is recorded at this time. Fanciful reconstructions derive it from the French de Campo Bello, but the likely source is the caimbeul, an Early Modern Irish or Gaelic by name meaning wry mouth, crooked mouth or twisted mouth.

Regarding the earlier ancestors of Clan Campbell, there is good evidence that the Campbells themselves traced their descent from an earlier kindred known as the Mac Duibne, or perhaps the Uí Duibne. It has been suggested that the family's early landholdings, around Menstrie, and in Cowal, were related to the partition of the Mormaerdom of Mentieth in 1213, and that Gilleasbuig may have been a kinsman of Mormaer Muireadhach Mór. The lands around Loch Awe, which would later form the core of their possessions, were not held at an early date.

The name begins to be established in Argyll at the end of the 13th century, as followers of the Earl of Lennox, with Campbells owning lands in Kintyre and the famous warrior Cailean Mór (Great Colin) knighted (1280) and established at Loch Awe. Cailean Mór's older brother established at Strachur forming the oldest branch of Clan Campbell, see Campbell of Strachur.

Between 1200 and 1500 the Campbells emerged as one of the most powerful families in Gaelic speaking Scotland, dominant in Argyll and capable of wielding a wider influence and authority in the Hebrides and western Highlands.