“Avoir l’esprit d’escalier” - or sometimes “avoir l’esprit de l’escalier” is yet another weird French idiom. Literally, it means to have the wit of the staircase. So it means nothing really!
Synonyms of "Avoir l'Esprit d'Escalier" in French and English
In English, you sometimes call this “escalator wit”, or afterwit. It means to think of a witty comeback, but only after the fact.
To say to make a witty comeback (something the French really admire and are trained to do as part of our national sport: arguing and debating), we use the expression “avoir de la répartie”. So here, we could say “manquer de répartie”, “ne pas savoir répliquer sur le moment”, “perdre ses moyens”.
Example of Escalator Wit in French and English
Moi, je manque cruellement de répartie. Quand je me sens attaquée, je perds tous mes moyens, je bredouille... et puis quand je suis rentrée chez moi, je trouve plein de répliques fantastiques. J'ai vraiment l'esprit d'escalier.
I desperately lack the ability to make witty comebacks. When I feel threatened, I lose my cool, I stutter... and once I'm back home, I find lots of great comebacks. I really have an escalator wit.
Origin of the French Idiom “Avoir l’Esprit d’Escalier”
The philosopher Diderot wrote around 1775: “« ...l'homme sensible comme moi, tout entier à ce qu'on lui objecte, perd la tête et ne se retrouve qu'au bas de l'escalier ». Which translates to: “The sensitive man such as myself, entirely absorbed by things that are being objected to him, loses his mind and recovers it only at the bottom of the stairs”. He meant that if someone opposed him in a conversation, he was so upset by it that he couldn’t concentrate anymore, and that it’s only once he had left, and reached the bottom of the staircase (therefore too late), that he could come up with a good answer.
French stairs
Speaking of "l'escalier", remember French people do not count their stairs the way Americans do.