composure (n.)youdaoicibaDictYouDict[composure 词源字典]
c. 1600, "composition" (also, in early use, with many senses now given to compound), from compose + -ure. Sense of "tranquility, calmness" is first recorded 1660s, from composed "calm" (1620s). For sense, compare colloquial to fall apart "to lose one's composure."[composure etymology, composure origin, 英语词源]