What does Jiao Da's climbing ash mean in A Dream of Red Mansions?

Climbing ash is a common saying, also called "picking up ash". Refers to improper sexual relations between father-in-law and daughter-in-law.

Why is the incest of Weng's wife called "climbing ash"?

One theory is that this proverb comes from Wang Anshi's story: Wang Anshi's son Wang (under the rain, Pang) died in his early years, and his wife was widowed and built a small building to live in. Wang Anshi often visits her out of concern for her daughter-in-law. The daughter-in-law misunderstood her father-in-law's meaning and thought that Wang Anshi had ulterior motives, so she wrote poems on the wall to show her mind. Wang Anshi was embarrassed to see this poem, so he scraped the dust off the wall with his nails. In this way, there is a saying of "picking up ashes" outside.

Obviously, this legend is far-fetched, probably fabricated by political opponents to slander Wang Anshi.

Another way of saying it is: "climbing ash" is homophonic. Climbing the dust will pollute the knees, and the homonym of "dirty knees" and "dirty daughter-in-law" originated from Li Tan in Qing Dynasty: "Vulgarity is a prostitute's code word, and the knee daughter-in-law is homonym. Squatting on the ash will dirty your knees. "

This statement seems credible. However, it is still difficult to justify: "climbing ash" is impossible in life. And why do those who "pick up dust" have to get their knees dirty?

Wang Youguang said another thing in the Qing Dynasty. In Wu Lian, Wang talked about the origin of "picking up ashes": in the past, temples were everywhere, and incense was particularly prosperous. In order to worship ghosts and gods, people often burn a lot of paper money coated with tin foil. Over time, there are more and more tin ashes, and the temple owner can sell tin ashes at a good price. As soon as the news came out, insatiable people often went to the temple to steal tin ash. "Picking up ashes", stealing tin, tin, and daughter-in-law are homophonic and thought to be code words.

It seems that Wang Youguang's explanation has some truth. The purpose of "picking up ashes" is to steal tin, while "tin" and "daughter-in-law" are homophonic, and "stealing tin" is changed to "stealing daughter-in-law", which is the origin of the word "picking up ashes".