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.

What does de grace mean?

De Grace Name Meaning

French (Degrâce): habitational name for someone from La Grâce in Marne.

Is coup de grace legal in war?

At Agincourt in 1415, Henry V ordered a coup de grace for severely wounded French soldiers. Today, this would be a war crime: the laws of war mandate caring for the wounded and prohibit mercy killing. ... Under the laws of war, the lawfulness of targeting a foreign leader outside of an ongoing armed conflict is dubious.