Have you ever wondered where the phrase came from?  I had an epiphany moment when I was baking cookies a month ago, then forgot about it until I again baked cookies yesterday.  It was then that I realized if you place the balls in rows of 3, then 2, then 3, then 2, then 3 on a regular cookie sheet to leave room for expansion, you can fit exactly 13 cookies on the sheet!  Voila!! A baker’s dozen!!! I perhaps could have discovered this by looking it up on Google, but much more fun to discover such facts on your own!

Or, for more information, look here: https://judydykstrabrown.com/2016/05/16/the-truth-about-the-bakers-dozen/