The following is taken from The Playing-Card, Volume XXV, number 3, p. 120.

From “The Official Encyclopedia of Bridge, 5th edition” (American Contract Bridge League):

A term applied to the 9 of diamonds, for which various explanations are given, none completely authoritative. The Bridge Magazine once listed six possible origins for the term as follows:

  1. That in the once popular round game ‘Pope Joan’, the 9 of diamonds was called the Pope, the antichrist of Scottish Reformers.
  2. That the 9 of diamonds was the chief card in the game ‘cornette’, introduced into Scotland by the unhappy Queen Mary.
  3. That ‘Butcher’ Cumberland wrote the orders for the Balle of Culloden, 1746, on the back of the card. This is very doubtful.
  4. That the order for the Massacre of Glencoe (1692) was signed on the back of this card.
  5. That the dispositions for the fatal field of Flodden (1513) were drawn up on it by James IV of Scotland.
    Both these last have only the slightest authority.
  6. That it is derived from the nine lozenges that formed the arms of the Earl of Stair, who was especially loathed for his connection with the Massacre of Glencoe and the union with England (1707).

The following comments are to be found in the “Dictionary of Phrase and Fable”, Dr Ebenezer Cobham Brewer, 1870, revised edition, Ivor H. Evans, 1981:

The Curse of Scotland. The nine of diamonds. The phrase seems to be first recorded in the early 18th century, for in Houston’s Memoirs (1715-1747), we are told that Lord Justice Clerk Ormistone became universally hated in Scotland, and was called the Curse of Scotland; and when ladies encountered the nine of diamonds at cards they called it Justice Clerk. Among the suggested origin of the phrase are:

  1. It may refer to the arms of Dalrymple, Earl of Stair (see (6) above).
  2. as in point (2) above
  3. as in point (3) above
  4. The word ‘curse’ is a corruption of cross, and the nine of diamonds is so arranged as to form a St. Andrew’s Cross; but so are the other nines.
  5. as in point (5) above
  6. Grose says somewhat inaccurately in his Tour Thro’ Scotland (1789); “Diamonds… imply royalty… and every ninth king of Scotland has been observed for many ages to be a tyrant and a curse to the country.”

The Curse os Scotland is also described in All Things Georgian (with many illustrations).