late 14c., "emit from a confined space," probably a shortening of Old French eventer "let out, expose to air," from Vulgar Latin *exventare, from Latin ex- "out" + ventus "wind" (see wind (n.1)). Sense of "express freely" first recorded 1590s. Sense of "divulge, publish" (1590s) is behind phrase vent one's spleen (see spleen). Related: Vented; venting.
"hole, opening, outlet," 1560s, from vent (v.). Meaning "action of venting" is recorded from 1550s.
An opening into a cavity or canal, especially one through which contents are discharged.