'assize' originates from Old French, specifically the word 'assise', ultimately from medieval Latin 'assisa' (past participle formation related to Latin 'assidere' meaning 'to sit beside' or 'to sit'), where the root referred to a 'sitting' or 'session'.

'assize' changed from Old French 'assise' / medieval Latin 'assisa' (meaning a 'sitting' or 'decree') into Middle English 'assise' and eventually the modern English 'assize', with senses narrowing to judicial sessions and statutory regulations.

Initially, it meant 'a sitting' or 'session' (and by extension a decree or regulation); over time it evolved to refer primarily to 'a judicial court session' and, historically, to certain statutes regulating weights and measures.