We know the verb abuse as a word meaning "to misuse," "to mistreat," or "to revile." But when disabuse first appeared in the early 17th century, there was a sense of abuse, now obsolete, that meant "to deceive." Sir Francis Bacon used that sense, for example, when he wrote in 1605, "You are much abused if you think your virtue can withstand the King's power." The prefix dis- has the sense of undoing the effect of a verb, so it's not surprising that disabuse means "to undeceive." English speakers didn't come up with the idea of joining dis- to abuse all on their own, however. It was the French who first appended their prefix dés- to their verb abuser. English disabuse is modeled after French désabuser.