arsenic [LME] The chemical element arsenic is a brittle steel-grey substance with many highly poisonous compounds, but its root word means ‘gold’. In English the word first referred to a compound of arsenic called arsenic sulphide or yellow orpiment, which was used as a dye and artist’s pigment. The word comes from Greek arsenikon but before that was probably transmitted via a Semitic language from a lost Persian word which shared the same base as Avestan zaranya- ‘gold’.