vacuous (adj.)youdaoicibaDictYouDict[vacuous 词源字典]
1640s, "empty" (implied in vacuousness), from Latin vacuus "empty, void, free" (see vacuum (n.)). Figurative sense of "empty of ideas, without intelligent expression" is from 1848. Related: Vacuously.[vacuous etymology, vacuous origin, 英语词源]