Inane, as a noun, means “something that is empty or void, esp. the void of infinite space.” Similarly, the adjective form means “empty; void” or “lacking sense, significance, or ideas; silly”.
It comes from Latin “inanitatem ‘emptiness,’ from inanis ‘empty, void, worthless, useless’”, according to the Online Etymology Dictionary.
I like this word for some reason – maybe because it sounds like insane. Or maybe I just like its comically snobbish tone: “Oh, stop your inane ramblings already!”