'canonist' originates from Medieval Latin and Old French, specifically Medieval Latin 'canonicus' and Old French 'canoniste', where the Greek root 'kanon' meant 'rule' or 'measuring rod'.

'canonist' developed via Old French 'canoniste' (from Medieval Latin 'canonicus' 'of or relating to a canon') and the noun-forming suffix (from Late Latin/Old French '-ista'/'-iste'), eventually becoming the modern English noun 'canonist'.

Initially it referred more broadly to someone 'of or relating to a canon' (e.g., a cleric or member of a chapter governed by canons); over time it narrowed to mean specifically 'a specialist or lawyer in canon law'.