After searching for vocabs and etymologies in wiktionary I translated it only myself and I've got " gratiae colaphus "
Is it correct? Or should I use "misericordiae" for "gratiae"? Or there is any classical translations that latin authors used for this?
According to Collins Dictionary, coup de grâce means:
The French word grâce conveys the idea that it's a blow of mercy (perhaps as a euphemism), i.e., with the purpose of putting someone out of their misery.
However, it's often used simply to mean a death blow, and it's not easy to capture the full meaning of coup de grâce in Latin with the same conciseness.
So here's a translation for just death blow:
plaga mortifera
This is actually an expression used by Cicero:
mortiferam plagam inflixisses auguratus tui
(you had added the deadly blow of your augurship)
If it's important to convey the idea of mercy as well, I believe the best way to do that would be to add an adjective:
plaga mortifera misericors
You might be able to use just plaga misericors, but I'm not sure that it would be as clearly understood.
Smith's has this:
finishing-stroke: extrema sive ultima manus : to give the f. to the war, bello extremam m[anum] imponere, Virg. Aen. 7,572. Phr.: to put the f. to a war, bellum commissum ac profligatum conficere, Liv. 21,40, extr.: to a work, opus coeptum profligatumque perficere, Aug. in Mon. Ancyr.
While profligatum [per/con]ficere is fine, keeping manus in the translation retains the coup imagery, since coup is primarily French for "blow" (as in an attack with the hands, a punch).
In addition to the excellent answers already given, Pinkster's dictionary mentions two interesting expressions, for which I have also found quotations:
- in mortem destringere ferrum: "to draw the sword for the coup de grâce"
Tacitus, Annales 14.8.1.22:
Circumsistunt lectum percussores et prior trierarchus fusti caput eius adflixit. Iam in mortem centurioni ferrum destringenti protendens uterum 'ventrem feri' exclamavit multisque vulneribus confecta est.
"Around her bed stood the assassins, and first the trierarchus injured her head with his club. To the centurion, who drew his blade for the coup de grâce, she exclaimed, while extending her womb, 'hit my belly', and she was finished off with many wounds." (Agrippina knew that the killers had been sent by Nero, the child she had borne.)
- causam publicam perimere: "to give the coup de grâce to the cause of the State"
Cicero, Pro Sestio 49.1:
Haec ego et multa alia cogitans hoc videbam, si causam publicam mea mors peremisset, neminem umquam fore qui auderet suscipere contra improbos civis salutem rei publicae; ...
"...if my death should have dealt the final blow to the cause of the State..."
In addition to Expedito Bipes' excellent answer, if your context is “to give someone the coup de grâce,” you can use the idiom aliquem conficere, e.g.
Venator leonem confecit.
The hunter finished the lion off.
No implied notion of mercyfulness, obviously.
It can also be used of inanimate objects, but note that conficio has a range of meanings, and especially with inanimate objects, some context might be needed to make clear you are talking about a destructive (rather than constructive) type of “completion,” so to speak.
