Why is granny cake called granny cake?

According to legend, in the early years of the Ming Dynasty, the rulers of the Yuan Dynasty constantly levied various taxes on the people, and the people were severely oppressed and plundered. There have been many uprisings all over the country, among which the most representative team is the rebel army led by Zhu Yuanzhang, and Zhu Yuanzhang's wife Ma Shi is a very clever person. At the beginning of the uprising, because of the frequent wars at that time, the army had to run around and carry dry food. So the horse came up with something to eat, such as wheat and wax gourd, mixed them together, ground them into powder, made them into cakes and distributed them to the sergeant. It is not only convenient to carry, but also can be eaten anytime and anywhere, which is of great help to marching operations. Because the cakes made from this mess are unpalatable, smart people update their methods on the basis of this kind of cake. Finally, people found that cakes made of sugar wax gourd, wheat flour, cake powder, maltose, sesame and other raw materials are very delicious, sweet and delicious, and they are the ancestors of the old lady's cakes.