quietus (n.)youdaoicibaDictYouDict[quietus 词源字典]
"discharge, clearing of accounts," 1530s, short for Medieval Latin phrase quietus est "he is quit" (see quit). Hence, "death" (i.e. "final discharge"), c. 1600. Latin quies also was used for "the peace of death."[quietus etymology, quietus origin, 英语词源]