The title Duke of Buccleuch (icon), formerly also spelt Duke of Buccleugh, was created in the Peerage of Scotland

Peerage of Scotland

The Peerage of Scotland is the division of the British Peerage for those peers created in the Kingdom of Scotland before 1707. With that year's Act of Union, the Kingdom of Scotland and the Kingdom of England were combined into the Kingdom of Great Britain, and a new Peerage of Great Britain was...

 on 20 April 1663 for the Duke of Monmouth

James Scott, 1st Duke of Monmouth

James Scott, 1st Duke of Monmouth, 1st Duke of Buccleuch, KG, PC , was an English nobleman. Originally called James Crofts or James Fitzroy, he was born in Rotterdam in the Netherlands, the eldest illegitimate son of Charles II and his mistress, Lucy Walter...

, who was the eldest illegitimate son of Charles II of Scotland, England, and Ireland

Charles II of England

Charles II was monarch of the three kingdoms of England, Scotland, and Ireland.Charles II's father, King Charles I, was executed at Whitehall on 30 January 1649, at the climax of the English Civil War...

 and who had married Anne Scott, 4th Countess of Buccleuch.

Anne was created Duchess in her own right along with her husband, so that the title was unaffected by Monmouth's attainder

Attainder

In English criminal law, attainder or attinctura is the metaphorical 'stain' or 'corruption of blood' which arises from being condemned for a serious capital crime . It entails losing not only one's property and hereditary titles, but typically also the right to pass them on to one's heirs...

 of 1685. It passed on to his descendants, who have successively borne the surnames Scott, Montagu-Scott, Montagu Douglas Scott and Scott again.