زرنیخ

The word 'arsenic' travels from Persian zarnīkh — compounded from zar (gold) and nīkh (a suffix denoting a substance or color) — through Greek arsenikon and Latin arsenicum before entering English. The substance that ancient and medieval chemists called arsenikon was arsenic trisulfide (As₂S₃), also known as orpiment, a vivid golden-yellow mineral valued as a pigment and used in medicines, dyeing, and tanning. The golden color was the defining feature: zar (gold) gives Persian the word for this yellow substance, and the connection between arsenic and gold was both visual and alchemical — alchemists believed arsenic compounds might be intermediaries on the path to transmuting base metals into gold.

The Greek word arsenikon, which the Romans borrowed as arsenicum, has been debated by etymologists. One tradition connects it to Greek arsen (male, potent, strong), linking the word to ideas of the substance's power. But modern etymologists have largely converged on the Persian zarnīkh as the source, noting that arsenikon appears in texts describing trade goods from the East, and that the Persian term predates the Greek. The path from zarnīkh to arsenikon is explained as a folk-etymological reshaping by Greek speakers who heard the Persian word and assimilated it to their own arsen. This kind of phonetic reinterpretation — where a foreign word is reshaped to sound like a familiar word in the borrowing language — is common in the history of chemical terminology.

The deadly property of arsenic compounds was known in antiquity, but the mineral name 'arsenic' was applied to the yellow sulfide mineral long before the white trioxide became the dominant form in European usage. Medieval and early modern chemists distinguished 'yellow arsenic' (orpiment), 'red arsenic' (realgar), and 'white arsenic' (the oxide). By the time 'arsenic' entered English in the 14th century through Old French arsenique, it was beginning to primarily denote the deadly white form. Arsenic poisoning became notorious in Renaissance Italy and 18th-century France — it was called 'inheritance powder' because it facilitated the transfer of estates — and by the 19th century 'arsenic' in common English usage meant exclusively the poison.