'inactivate' originates from Latin and English elements, specifically the prefix 'in-' (from Latin) meaning 'not' combined with 'activate' (from Late Latin 'activare', from Latin 'activus' meaning 'active').

'inactivate' was formed in modern English by adding the negative prefix 'in-' to the verb 'activate' (which itself came into English via Late Latin 'activare' and Old French influences), producing the meaning 'to make not active'.

Initially and historically it has meant 'to make not active' (often in technical or scientific contexts); this basic meaning has been maintained into current usage, though its application has broadened (e.g., to devices, enzymes, or vaccines).