Is there an English term for "L'esprit de l'escalier"?

Solution 1:

I've only ever known it in its literal translation as staircase wit.

Solution 2:

English speakers sometimes call this escalator wit.

Afterwit can also be a synonym for this concept, with forewit as its antonym.

Definition of afterwit in Wiktionary:

1. Wisdom which comes after the event.

   After-wits are dearly bought, Let thy fore-wit guide thy thought. ― Southwell.
   There is no recalling what’s gone and past; so that afterwit comes too late, when the mischief is done. — L’Estrange

2. The lack of forethought.

   This week I am fearing afterwit as I create the outline for my next novel ... — Grace Tierney, 2010
   One good forewit is worth two afterwits. — Saying/Proverb

3. A good comeback one thinks of after leaving a social gathering.