Because you leave the dough overnight in the refrigerator - before we had electricity in our homes, people had iceboxes to keep things cool instead. u003ca href=u0022https://americanhistory.si.edu/blog/ice-harvesting-electric-refrigerationu0022 target=u0022_blanku0022 rel=u0022noreferrer noopeneru0022u003eThe National Museum of American history explains moreu003c/au003e.