The story
- French · calque ofquatrième mur
- English todayfourth wall
A reference to the three walls of a box set, with the fourth wall being the imaginary wall separating the performers from the audience. Coined by philosopher and art critic Denis Diderot in 1758 and thus a calque of French quatrième mur.
Etymology from Wiktionary, CC BY-SA 4.0.