amalgamate: [17] Amalgamate is a derivative of amalgam, a term for an alloy of mercury and another metal (now usually used for tooth fillings) borrowed into English from French or medieval Latin in the 15th century. Latin (amalagama) probably acquired the word from the Greek adjective málagma ‘softening’, a derivative of the verb malássein ‘soften’, which is a distant relative of English malleable (see MALLET). [amalgamate etymology, amalgamate origin, 英语词源]
1650s, back-formation from amalgamation, or from adjective amalgamate (1640s) from amalgam. Originally in metallurgy; figurative sense of "to unite" (races, etc.) is attested from 1802. Related: Amalgamated; amalgamating. Earlier verb was amalgamen (1540s).