The nine of diamonds playing card is called the "Curse of Scotland" for several possible historical and folklore reasons, with no single definitive explanation. The most widely accepted theory is that it refers to Sir John Dalrymple, 1st Earl of Stair, a controversial figure involved in the 1692 Glencoe Massacre. His family coat of arms featured nine diamond-shaped lozenges, resembling the nine of diamonds card, and he was widely hated in Scotland, which likely led to the card being nicknamed the "Curse of Scotland".

Other explanations include:

• A tale of the Duke of Monmouth or the Duke of Cumberland writing orders on a nine of diamonds card before battles (Bothwell Bridge 1679 or Culloden 1746), though these stories are considered unlikely as the nickname predates some of these events.

• The card game Pope Joan, where the nine of diamonds is called "the Pope," seen as a curse by Scottish reformers.

• Some folklore claims about stolen diamonds from the Scottish Crown Jewels or a connection to every ninth Scottish king being a tyrant.

The phrase "Curse of Scotland" is first seen in print in the early 18th century, and the ties to Dalrymple's hated legacy remain the strongest historical link to the card's ominous nickname.