Thanks to Technologies du langage, I now know why writers of poison-pen letters are called corbeaux (crows) in French.
Between 1917 and 1922, a woman wrote anonymous letters to several people in Tulle, a small town in Corrèze. Everyone started suspecting everyone else, and paranoia set in. She was finally prosecuted, and Le Matin newspaper described her as a crow (she was in mourning and wearing black) : "un oiseau funèbre qui a replié ses ailes" (a lugubrious bird with folded wings). Apparently, this image directly inspired French director Clouzot’s choice of title for Le Corbeau, the film he directed after these events. The film was a success, and 84 years later, corbeaux are still active in France