Unhappen

Part of speech: verb

Definitions

1. To become as though something had never taken place, undoing the fact that it occurred
2. Describing an event being erased so that it is no longer true that it ever came about
3. Having something that already occurred be treated as if it never took place at all

Etymology: "Unhappen" is a plain formation: the prefix "un-", meaning "reverse" or "undo," attached to the verb "happen." The result describes undoing an event so that it is treated as though it never occurred. English has long used "un-" this way with verbs, as in "undo," "unsay," and "unwrite," so the word follows a familiar pattern rather than a special invention. The base verb "happen" comes from the Middle English "happen," formed from "hap," meaning chance or luck, which is what gives "happen" its sense of something falling out by chance. Adding "un-" to a verb meaning "to occur" produces a verb meaning to make an occurrence stop having happened, which is why the word is most often used in discussions of time, fiction, and what might have been done differently.