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.
<a href="https://www.etymonline.com/word/ventilator">Etymology of ventilator by etymonline</a>
Harper, D. (n.d.). Etymology of ventilator. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ventilator