[Lee Stewart]

Bakers in medieval England are thought to have come up with the idea of tossing in an extra roll or loaf of bread to make sure their customers were happy. While 12 eggs are easy to quantify, baked goods can turn out all different sizes because of differences in how much the dough rises. Plus, many bakers didn't have accurate scales to weigh their flour, according to Britannica. Being accused of cheating could result in punishments including flogging, so bakers hedged their bets and included 13 (or sometimes 14) items to make sure nobody complained.