From Latin 'advenire' (to arrive) via French 'aventure' (chance) — the 'd' was added by scribes reconnecting to Latin.
An unusual, exciting, and potentially hazardous experience or activity; a daring enterprise; to engage in hazardous or exciting activity.
From Old French 'aventure' (chance, fate, what comes to one), from Vulgar Latin '*adventūra' (what is about to happen), from Latin 'adventūrus,' future active participle of 'advenīre' (to arrive, come to), from 'ad-' (to) + 'venīre' (to come). The Latin 'venīre' derives from PIE *gʷem- (to come, to go). The initial 'd' in English was inserted in the 15th–16th century by association with Latin 'adventus,' though the Old French form lacked
The word entered English as 'aventure' without the 'd' — that letter was added centuries later by scholars who wanted to reconnect the word with its Latin ancestor 'adventus.' This same hyper-correction happened to several English words: 'advance' (from 'avance'), 'admiral' (from 'amiral'). In some cases the inserted letter stuck; in others