plenum (n.)youdaoicibaDictYouDict[plenum 词源字典]
1670s, "filled space" (opposite of vacuum), from Latin plenum (spatium) "full (space)," neuter of adjective plenus "complete, full" (see plenary). The meaning "of a full assembly of legislators" is first recorded 1772.[plenum etymology, plenum origin, 英语词源]