Things I Learned Today #1: “blackmail” is a Scottish word, and the Highland Scots invented the protection rackets.
World Wide Words: Blackmail
The mail in blackmail (at various times also spelled maill, male and in other ways) is an old Scots word for rent. This was usually paid in what was often called white money, silver coins. It comes from Old Norse mal, meaning an agreement, later a contract, and then the payment specified by the contract.In the sixteenth and seventeenth centuries chieftains in the highlands of Scotland and along the border between Scotland and England ran protection rackets in which they threatened farmers with pillage and worse if they didn’t pay up. This amounted to an informal tax or extra rent and the farmers, with twisted humour, thought of it as the opposite of the legitimate white money or white mail that they paid. Black has for many centuries been associated with the dark side of human activities, hence blackmail.
