What is the origin of the idiom "baker's dozen" and when to use it?

The idiom "baker's dozen" has its origins in medieval England when there were strict laws governing the weight and pricing of bread. To avoid the risk of underweight loaves and potential penalties, bakers would often add an extra loaf to a dozen (which originally meant 12) to ensure they met the required weight. This practice became customary, and "baker's dozen" came to mean 13 rather than 12. This expression is used to describe a group of 13 items or things. It is often used when someone wants to emphasize that they are providing a little extra or going beyond the expected quantity, similar to the original practice of bakers adding an extra loaf to a dozen.