Oh! That would explain why the Marauders Map in Harry Potter says it's made by "Mssrs. Moony, Wormtail, Padfoot and Prongs." I figured it was an abbreviated version of "monsieurs." In the movie Harry pronounces it "messers." I don't know if that's right or for realism they let a 13-year-old pronounce it as he would guess. This sounds strange to me. It reminds me of the German "Messer" which means knife.