What is the origin of peradventure?

As an adverb, peradventure means “maybe, possibly, perhaps”; as a noun, peradventure means “chance, doubt, or uncertainty.” Peradventure comes from Middle English paraventur(e), peradventure (and 20 other spelling variants), from Old French and Anglo-French par aventure, peradventure. Par is an 11th-century development of Latin and Old French per “through, by, by means of.” Adventure comes from Middle English aventure, avento(u)r, adventure, from Old and Middle French aventure “destiny, fate, chance; risk, peril,” from Medieval Latin (rēs) adventūra “(thing) about to come, (thing) going to happen.” Adventūra is the future participle of the Latin verb advenīre “to come to, arrive at, reach; (of conditions) to arise, develop; (of possessions) to come into the hands of.” Peradventure entered English about 1300.