late 14c., "yellow arsenic, arsenic trisulphide," from Old French arsenic, from Latin arsenicum, from late Greek arsenikon "arsenic" (Dioscorides; Aristotle has it as sandarake), adapted from Syriac (al) zarniqa "arsenic," from Middle Persian zarnik "gold-colored" (arsenic trisulphide has a lemon-yellow color), from Old Iranian *zarna- "golden," from PIE root *ghel- (2) "to shine," with derivatives referring to bright materials and gold.
The form of the Greek word is folk etymology, literally "masculine," from arsen "male, strong, virile" (compare arseno-koites "lying with men" in New Testament) supposedly in reference to the powerful properties of the substance. As an element, from 1812. The mineral (as opposed to the element) is properly orpiment, from Latin auri pigmentum, so called because it was used to make golden dyes. Related: Arsenical.