vacuity (n.)youdaoicibaDictYouDict[vacuity 词源字典]
late 14c., "hollow space," from Latin vacuitas "empty space, emptiness, absence, vacancy, freedom," from vacuus "empty" (see vacuum (n.)). Originally in anatomy. Meaning "vacancy of mind or thought" is attested from 1590s.[vacuity etymology, vacuity origin, 英语词源]