'initiator' originates from Latin, specifically the verb 'initiare' and the noun 'initium', where 'init-' related to 'beginning' or 'entrance'.

'initiator' developed from Late Latin/Medieval Latin formations based on 'initiare' and entered Middle English via Old French and Latin-derived formations, eventually becoming modern English 'initiator' (with the agentive suffix '-or').

Initially associated especially with rites of introduction or formal beginnings ('one who initiates' a ceremony), the meaning broadened to include any person or thing that starts or triggers a process or reaction.