D. Watkin (1986)
Quincunx is also used for an arrangement of five objects with four at the corners of a square or rectangle and the fifth at its centre, used for the five on a dice or playing card, and in planting trees (this sense, which is also found in Latin, apparently derives from the use of five dots or dashes, arranged in this way, to denote five twelfths of an as), an ancient Roman copper coin.
The word is Latin, and means literally ‘five twelfths’.
An astrology term denoting planets at a distance of five signs of 150 degrees from each other. The term was once generally used to denote a disposition of five objects (especially plants or trees) placed so that there is one in each corner of a square or rectangle with the fifth in the center. The use of the quincunx in various aspects throughout history was exhaustively discussed by the English physician and author Sir Thomas Browne (1605-1682) in his book The Garden of Cyrus (1658).