'assay' originates from Anglo-Norman and Old French, specifically the words 'assai' and 'essai', where the sense was 'trial' or 'test' (related to trying or attempting). The Old French terms derive from a Vulgar Latin form *exagium.

'assay' changed from Old French 'essai' and Anglo-Norman 'assai' into Middle English forms such as 'assayen' (to try or test) and eventually became the modern English word 'assay'.

Initially, it meant 'a trial' or 'an attempt'; over time it specialized to mean 'a test or analysis to determine composition or quality', especially in metallurgy and the sciences.