Louis Maigret (or Meigret) was the author of the Traité de la Grammaire française, which was published in 1550. This was the first grammatical description of (Middle)French.
References
Malmberg, Bertil (1991). Histoire de la linguistique: de Sumer à Saussure (1. éd ed.). Paris: Presses universitaires de France. ISBN9782130433576.