inane (adj.)

c. 1600, "emptiness, hollowness," literal and figurative, from French inanité (14c.) or directly from Latin inanitas "emptiness, empty space," figuratively "worthlessness," noun of quality from inanis "empty, void; worthless, useless," a word of uncertain origin. De Vaan writes that "The chronology of attestations suggests that 'empty, devoid of' is older than 'hollow'." Meaning "silliness, want of intelligence" is from 1753.