The Wit of the Staircase:
From the French phrase 'esprit d'escalier,' literally, it means 'the wit of the staircase', and usually refers to the perfect witty response you think up after the conversation or argument is ended. "Esprit d'escalier," she replied. "Esprit d'escalier. The answer you cannot make, the pattern you cannot complete till aterwards it suddenly comes to you when it is too late."