www.alphadictionary.com

This means empty, from the Latin word, vacuus, which means..........empty. And, of course, a vacuum is..........empty! But, wait, there is more. "Vacuus" is related to "vacare", which means "be empty". But still more, as the Latin word vanus, for empty or void gave us "vain". Think of vain, vacuous persons, but then I repeat myself.

In play, I most often see the word used as you did referring to empty headed people, or air-heads.