missive (n.)youdaoicibaDictYouDict[missive 词源字典]
mid-15c., "commandment," noun use of adjective (mid-15c.) meaning "sent by superior authority," from Medieval Latin missivus "for sending, sent," especially in littera missiva "letters sent," from Latin missus, past participle of mittere "to send" (see mission).[missive etymology, missive origin, 英语词源]