Only recently, as a soapmaker, did I realize that what we were seeing back then was naturally occurring soap. The fat from the cooking meats had dripped down and mixed with the coals from the fire. And then

the rainwater acted to mix the animal fat with the highly alkaline substance in the coals. This highly alkaline substance in the coals was produced by the burning wood. This substance is referred to by soapmakers as potash. Potash was commonly used by soapmakers for many years in the distant past.