'argentous' originates from Latin, specifically the word 'argentum', where the root 'argent-' meant 'silver'.

'argentous' was formed in English by adding the adjectival suffix '-ous' to 'argent'. 'Argent' passed into Middle English from Old French 'argent', which ultimately came from Latin 'argentum'.

Initially the root referred specifically to the metal 'silver'; over time the derived adjective came to be used more generally for 'silvery' appearance or for containing silver, and in heraldry for the tincture argent.