Ever thought of the perfect comeback, but thought of it way too late? Then you’ve got a case of staircase wit.
The logic behind this phrase is simple: you think of the perfect thing to say once you’re at the bottom of the stairs, leaving the injuring party behind. Diderot was the first to describe it in this way, in the 18th century text The Paradox of the Actor:
a sensitive man, such as myself, overwhelmed by the argument levelled against him, becomes confused and can only think clearly again [when he finds himself] at the bottom of the stairs
The French phrase that Diderot used, l’esprit de l’escalier, is where we get the English phrase.