Chocolate & Zucchini gives us "Casser du sucre sur le dos de quelqu'un." It means, literally, "breaking sugar on someone's back," or engaging in malicious gossip about someone. In other words: backbiting , which, come to think of it, is slightly food-related too, in a cannibalistic sort of way. For example : "Dès qu'il sortait, ses collègues se mettaient à casser du sucre sur son dos." ("The minute he was out the door, his coworkers would start breaking sugar on his back.") According to these sources , this idiom appeared in the late 19th century, and may derive from the older expressions "sucrer quelqu'un" , which meant mistreating someone, and " se sucrer de quelqu'un ," which meant taking someone for a fool. Sugar was then a symbol of wealth; why it was linked to such negative notions, however, is unclear. Em português, Cortar na Casaca, Cortar na Pele :)