Everything starts with the greek έπιούσιον. (1)
It has indeed been hard to translate as this word cannot be found anywhere else in other greek texts. Origenes suspected the Evangelists to have forged it… ex-nihilo… 🙂

One possible understanding is : what is necessary / suffices to keep our existence going and not only today but tomorrow and other days in the future.

This understanding leading to the vulgate’s latin translation :

• Panem nostrum quotidianum (Saint-Luc)

Keeping strict latin vocabulary and grammar, Luc’s phrase should translate in french :

Notre pain quotidien

or, alternatively

Notre pain de chaque jour

Chaque jour and actually not ce jour

However, as it appeared somehow strange to ask for having now altogether the bread of tomorrow and the one of following days in the future… chaque was changed to ce. asking then today for todays’bread only.

^{1 : I know I should copy the entire sentence however, I am too lazy to key in non roman chars with that suboptimal editor.}