adventure (n.)
c.1200, auenture "that which happens by chance, fortune, luck," from Old French aventure (11c.) "chance, accident, occurrence, event, happening," from Latin adventura (res) "(a thing) about to happen," from adventurus, future participle of advenire "to come to, reach, arrive at," from ad- "to" (see ad-) + venire "to come" (see venue).

Meaning developed through "risk/danger" (a trial of one's chances), c.1300, and "perilous undertaking" (late 14c.) and thence to "a novel or exciting incident" (1560s). Earlier it also meant "a wonder, a miracle; accounts of marvelous things" (13c.). The -d- was restored 15c.-16c. Venture is a 15c. variant.
adventure (v.)
c.1300, "to risk the loss of," from adventure (n.). Meaning "to take a chance" is early 14c. Related: Adventured; adventuring.