Sourdough is a type of bread that has been made for centuries. It is made with a starter, which is a mixture of flour and water that has been fermented with wild yeast. The starter is used to leaven the dough, giving it a unique flavor and texture. The term 'sourdough' is derived from the MINER's practice of carrying a small amount of starter in a pouch around their neck while they worked. This starter was used to make bread, and over time it became known as 'sourdough'.