What's the difference? You're their all-time best seller

I was listening to NPR the other day and heard about this book on words that are extremely difficult to translate from one language to the other. One of the example the author found for French was "esprit de l'escalier" which I did not recognize right away, but eventually remembered to be indeed "l'esprit de l'escalier", you know, the comeback thought that crosses your mind and would have been extraodinarly a propos 2 minutes before in the heated discussion you just had but did not have the wittiness to find, that's having " l'esprit de l'escalier" or the wit as you march down the stairs.