Soup seed bread is a method of bread making that originated in Japan. Similar to mesquite, sourdough, or liquid bread, sourdough is added to some bread recipes to make the bread softer and more water-retentive. The word "yu" in Japanese means warm or thin dough. The word "yu" means boiling water, hot water, or hot spring. "Seed" means seed, variety, material, and noodle fertilizer (seed).