vaporous (adj.)

late 14c., from Anglo-French vapour, Old French vapor "moisture, vapor" (13c., Modern French vapeur) and directly from Latin vaporem (nominative vapor) "a warm exhalation, steam, heat," which is of unknown origin. Vapors "fit of fainting, hysteria, etc." is 1660s, from medieval notion of "exhalations" from the stomach or other organs affecting the brain.