It's probably a misspelling because "esprit d'escalier" actually means something in French!

Something like "рôte mal venu", je croix. (Mon francais est trés rouillé.) I hope we'll find out when trade paperback will be published: if they'll change "a" pour "o" then we'll be sure it was a misspelling.

That or Willow has studied old French when "écolier" was still "escolier".

Or her modern French turned into old French because or the unstable reality! :))))

(Really, the story becomes more and more campy with every issue)