Good question. It’s not really anything. It’s a word Nancy Silverton probably made up to describe this particular bit of bakery. However it resembles the French “crottin” as in crottin de Chavignol, probably the world’s most famous goat cheese. As for where that word came from, there’s some dispute over it. Some say that it comes from the Old French word crot, a short, round oil-burning lamp made from clay. That’s the uptown explanation. The downtown version posits that the word actually means “manure”, “dung” or “dropping”, specifically from a heard animal. Crotte is the word for that in French. Me, I’d just as soon not call these things “chocolate droppings”. I’m sure Nancy Silverton didn’t want to do that either, thus the creative license on the French.