Être aux cent coups = To be half mad (distracted) with anxiety; To be in the greatest difficulties.
C’est un coup qui porte = That is a home-thrust.
Avoir un coup de marteau = To be a little touched.
J’ai écrit trois lettres coup sur coup = I wrote three letters one after the other.
Un coup de sang = A rush of blood to the head.
Un coup de Jarnac = A treacherous blow; A blow below the belt.
[In a duel before the whole Court in 1547, Gui Chabot, Seigneur de Jarnac, wounded his adversary, La Châtaigneraie, with an unfair stroke. La Châtaigneraie refused to survive such an affront, tore off the bandages placed over his wound, and bled to death.]
Un coup de fouet = (lit.) A crack of a whip; (fig.) A sudden contraction of the muscles of the leg (or back).
Un coup d’état = A sudden, unexpected act of policy; A violent change in the Government (e.g. 18 brumaire 1799, or 2 décembre 1851).
Un coup de fion (fam.) = A finishing touch.