Because the ancients used Gleditsia sinensis to wash clothes in the Yellow River valley, and there were no Gleditsia sinensis trees in the Yangtze River valley, they found a tree with the same performance as Gleditsia sinensis, which can also wash clothes, but it is more plump than Gleditsia sinensis, so they named her Gleditsia sinensis, also called Gleditsia sinensis fruit.

Later, when artificial detergents were invented, the word "soap" was still used.

Therefore, although there is no thin soap, there is a non-fat soap, namely "Gleditsia sinensis".