coup de grâce

Borrowed directly from French and first appearing in English at the end of the 17th century, "coup de grâce" (literally, a "stroke of grace" or "blow of mercy") originally referred to a mercy killing, or the act of putting to death a person or animal who was severely injured and unlikely to recover. (In some contexts the term is used to refer to the final act of executing a convicted criminal.) Less than fifty years later, "coup de grâce" had come to mean "an act or event that puts a definite end to something." Other "coup" terms that have made the jump from French to English include "coup de main," for a sudden, forceful attack, and "coup d'état" for a violent overthrow of a government usually by a small group.