Origin of "blackmail"?

[Jinx]

Never thought about it before, but where does this term come from? it must have been slang for something, I WAG…

[Q.E.D]

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.

[Catalyst]

OED to the rescue:

@OED Online

[f. MAIL = rent, tribute.]

1. (Hist.) A tribute formerly exacted from farmers and small owners in the border counties of England and Scotland, and along the Highland border, by freebooting chiefs, in return for protection or immunity from plunder.

2. By extension: Any payment extorted by intimidation or pressure, or levied by unprincipled officials, critics, journalists, etc. upon those whom they have it in their power to help or injure. Now usu. a payment extorted by threats or pressure, esp. by threatening to reveal a discreditable secret; the action of extorting such a payment. Also fig.

3. (Law.) Rent reserved in labour, produce, etc., as distinguished from ‘white rents,’ which were reserved in ‘white money’ or silver. Obs. (Coke’s and Blackstone’s explanation of redditus nigri, which Camden appears to have taken for rents in ‘black money’ or copper.)

On preview, it seems I’ve been beaten to the punch, so … what he said.