Who is the French writer first used term essai to describe his nonfiction writing?

The French writer who first used the term "essai" (essay) to describe his nonfiction writing is Michel de Montaigne.

He published his collection of essays, titled "Essais", in 1580. This marked a significant moment in the history of the essay as a literary genre, as Montaigne's work established a new model for personal, reflective, and exploratory writing.