I bet the Romans made really good biscotti with honey, dates, raisins, and nuts!
Incredibly, the word lives on as «crostolo/crostoli» in Venice, a sweet pastry known as "angel wings" in English.
"crustulum" sounds nasty compared to "cookie." Kind of like British "biscuit." (No offense, friends across the pond.)
No offence taken sir, but we do also say 'cookie' when referring to the round type of biscuit with chocolate chips/raisins in them :)