'placater' originates from English, specifically from the verb 'placate', which ultimately derives from Latin 'placare', where 'plac-' meant 'to please' or 'to calm'.

'placate' entered English in the early 17th century from Latin 'placatus'/'placare', with influence via French forms; the agentive English noun 'placater' was later formed by adding the suffix '-er' to 'placate'.

Initially, Latin 'placare' meant 'to please or calm'; over time the sense developed into 'to soothe or appease (often by conciliatory action)', and 'placater' specifically denotes one who performs that action.