[4] Theories on the origin of the name vary; some arguing it stems from the Middle English: kerr which refers to brushwood, low lying grassland, marsh or fen.

[6] At this time, Cunninghame was under the control of de Morville who also maintained the nearby port of Irvine – one of Scotland's earliest capitals – as his military headquarters.

[8] Family tradition asserts the Norman origin for the chiefs comes from two brothers, Ralph and Robert (also called John), who came to Roxburgh from Lancashire.

[11] After Flodden, some of the Liddesdale clans put themselves under the Kerr of Ferniehurst's protection, but, in 1523, his castle was captured by an English force after a protracted defence.

[5] During the Scottish Civil War, Colonel Kerr supported the Covenanter commander, General David Leslie, Lord Newark, and took the Clan Mackenzie's Redcastle, demolished it, and hanged the garrison.

[5] He fought several duels throughout his military career but rose ultimately to the rank of general, and was appointed governor of Edinburgh Castle in 1745.

[5] The eldest of the brothers, Mark, Lord Kerr, later the fourth Marquess of Lothian, commanded three squadrons of government cavalry at the Battle of Culloden and survived to serve under the Duke of Cumberland in France in 1758.

[5] The Kerrs have typically been associated with left-handedness, and some of their buildings, such as Ferniehirst Castle, supposedly have turnpike stairs explicitly designed with this in mind,[14][15] though this is disputed.

A left-handed mercenary warrior could command a higher fee for his services, and those who fought under the Ferniehirst and Cessford banners were encouraged to fight "ker-handed".

[19] Castles that have been owned by the Clan Kerr include among others: The family crest comprises the Latin motto 'Sero Sed Serio' (late, but in earnest) with an image of the sun at its centre.

During four hundred years of cross-border invasions, feuding and lawlessness in the Scottish Borders, survival came to depend upon a shifting pattern of allegiances.

As the balance of the battle tipped in favour of the Scots, the Kerrs switched loyalties and turned their cavalry against the English, who had a low winter sun in their eyes,[20] and drove them from the field.