History of lye soap
Lye soap is something that has been around for innumerable generations. Back before things like this were mass produced, lye soap was made at home, with ingredients pulled from everyday activities. The lye was taken from burning wood in the fireplace, and the lard used was taken from butchered animals. There was a lot of hard work, and tons of mixing that went into making homemade lye soap. It was also a delicate process. If there was too much lye in the soap, and not enough lard, the soap would burn the skin on contact. If not enough lye was added to the mixture, it would never set. It was a long process, many times of just plain trial and error.
Resources for Lye soap, Candle and soap making and Lye soap uses