quincunx (n.) Look up quincunx at Dictionary.com
1640s, originally astrological, of planetary alignments, from Latin, literally "five twelfths" (especially "five unciae," that is, "five-twelfths of an as," the basic unit of Roman currency), from quinque "five" (from PIE root *penkwe- "five") + uncia "ounce; a twelfth part (of anything)," related to unus "one" (from PIE root *oi-no- "one, unique"). Applied, especially in garden design, to arrangements like the five pips on a playing card (1660s). Related: Quincuncial.