As the customer’s voice rose, the manager adopted a soothing, conciliatory [kənˈsɪliəˌtɔri] tone and promised that the situation would be remedied.

conciliatory
adj

Something described as conciliatory is intended to reduce hostility or to gain favor or goodwill.

The verb conciliate was borrowed into English in the mid-16th century and descends from the Latin verb conciliare, meaning “to assemble, unite, or win over.” Conciliare, in turn, comes from the noun concilium, meaning “assembly” or “council.”

English