'preventer' originates from English, formed by adding the agentive suffix '-er' to the verb 'prevent', which ultimately comes from Latin 'praevenire' (prae- meaning 'before' + venire meaning 'to come').

'preventer' developed in English from the verb 'prevent' (Middle English 'preventen'), itself borrowed via Old French 'prevenir' from Latin 'praevenire'; the English agentive suffix '-er' was attached to form 'preventer'.

Originally the Latin root conveyed 'to come before' or 'to anticipate'; over time the sense shifted toward 'to stop or hinder', and 'preventer' came to mean 'one that prevents' or 'something that prevents'.