 It is derived from Anglo-Norman "crust" (> English "crust") corresponding to French "croust".It is related to 18th century French "croustade" probably borrowed from Italian "crostata" (already mentioned 13th century), derived from "crosta" ("croûte" in French), more probably than Occitan "croustado" « tart ».Some other names for varieties of custard tarts in the Middle Ages were "doucettes" and "darioles".