As hundreds of thousands of people took to the streets across France this past weekend in support of student protesters, many displayed a somewhat mystifying rallying cry on their cardboard signs: “Bismillah, c’est les ténèbres.”

The phrase, a mashup of the Islamic blessing “In the name of God” and the French phrase “It’s the darkness,” may make little sense on the surface.

But it has become a symbol of a generational rift since young people began protesting last month against lackluster school resources — demonstrations that evolved into widespread unrest this past weekend.

The sentence seems to have first been used on Snapchat by someone who was seeking entry to a private chat room where student protest organizers gathered.…