affair: [13] Like ado, and of course to-do, affair originally meant literally ‘to do’. It was coined in Old French from the phrase à faire ‘to do’, and entered English via Anglo-Norman afere. The spelling affair was established by Caxton, who based it on the French model. The specific sense of a ‘love affair’ dates from the early 18th century. => fact[affair etymology, affair origin, 英语词源]