'assessory' originates from Medieval Latin, specifically the word 'assessorius' (from 'assessor'), where 'assessor' referred to an assistant or one who sits beside (an official) to help assess.

'assessory' changed from Medieval Latin 'assessorius' into Middle English as 'assessory' and continued into modern English as a rare or archaic term meaning 'auxiliary' or 'accessory'.

Initially, it meant 'pertaining to an assessor; serving as an assistant in assessment', but over time it evolved into the broader sense of 'secondary' or 'accessory' and is now largely rare or archaic in general use.