COIN (older forms of the word are coyne, quoin and coign, all derived through the O. Fr. coing, and cuigne from Lat. cuneus, a wedge), properly the term for a wedge-shaped die used for stamping money, and so transferred to the money so stamped; hence a piece of money. The form "quoin" is used for the external angle of a building (see Quoins), and "coign," also a projecting angle, survives in the Shakespearean phrase "a coign of vantage."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)