"process of replacing foul air in an enclosed place with fresh, pure air," 1660s, from Latin ventilationem (nominative ventilatio) "an exposing to the air," noun of action from past participle stem of ventilare (see ventilate).
early 15c., "to scatter, disperse (as the wind does)," from Latin ventilatus, past participle of ventilare "to brandish, toss in the air, winnow, fan, agitate, set in motion," from ventulus "a breeze," diminutive of ventus "wind" (from PIE *wē-nt-o‑ "blowing," suffixed (participial) form of root *we- "to blow").
Original notion is of cleaning grain by tossing it in the air and letting the wind blow away the chaff. Meaning "supply a room with fresh air" first recorded 1743, a verbal derivative of ventilation. Formerly with diverse slang senses, including "shoot" (someone), recorded from 1875, on the notion of "make holes in." Related: Ventilated; ventilating.
also loop-hole, mid-15c., from hole (n.). + Middle English loupe "narrow window, slit-opening in a wall" for protection of archers while shooting, or for light and ventilation (c. 1300), which, along with Medieval Latin loupa, lobia probably is a specialized word from a continental Germanic source, such as Middle Dutch lupen "to watch, peer." Figurative sense of "outlet, means of escape" is from 1660s.