'assayer' originates from Old French, specifically the word 'essayer'/'assaier', ultimately related to Vulgar Latin *exagiare and Latin 'exagium' (a weighing), where the root sense involved testing or weighing.

'assayer' changed from Middle English/Anglo-Norman forms such as 'assaiour'/'assaier' and eventually became the modern English word 'assayer'.

Initially, it referred specifically to weighing or testing metals (a technical process of assay); over time it broadened to mean examining or analyzing the quality or composition of substances, and a person who performs such tests.