'conciliate' originates from Latin, specifically the word 'conciliāre', where 'con-' meant 'together' and 'conciliāre' meant 'to bring together, to win over.'

'conciliate' passed into English via Medieval Latin/Old French forms (e.g. Medieval Latin 'conciliat-' / Old French 'concilier') and became the modern English 'conciliate' by the late Middle English period.

Initially it meant 'to bring together or unite (often by agreement or council) and to obtain favor'; over time the sense shifted toward 'to placate, reconcile, or gain goodwill,' which is the common contemporary meaning.