What does it mean that "the prime minister Hefei is thin and the farmer Changshu is barren"? What are the allusions?

In ancient times, due to political factors, cultural factors and other reasons, when addressing others, they often did not directly address each other by name, but used referring words to describe each other. For example, the famous saying that "the prime minister Hefei is thin and the farmer Changshu is barren" is a good example.

"Prime Minister Hefei is thin in the world, and farmer Changshu is barren in the world" was originally a couplet. The first couplet in the couplet refers to Li Hongzhang. Because Li Hongzhang is from Hefei, Anhui, people call him "Li Hefei" in his hometown. The first couplet means that Li Hongzhang's family is fat and everyone in the world is thin. The second couplet refers to Weng Tonghe. Because he is from Changshu, Jiangsu, people call him "Weng Changshu". The second couplet means that the Weng family has food to eat, but the land of the people all over the world is barren.

So where did this couplet come from?

In the late Qing Dynasty, Li Hongzhang and Weng Tonghe were officials in the same dynasty, but they had a bad relationship and often fought in officialdom. After a long time, the two always attack each other with political events. In the Sino-Japanese War, Weng Tonghe was defeated because of his narrow mind. Afterwards, Empress Dowager Cixi investigated the responsibility, and Weng Tonghe tried every means to blame Li Hongzhang for the failure. He believes that Li Hongzhang's accumulation of wealth and deduction of military expenses in the war led to the tragic death of soldiers and the failure of the war, and should be executed immediately. In fact, the real reason is that Weng Tonghe and others cut Li Hongzhang's military expenditure for Beiyang Navy, which led to the shortage of equipment in the war and was doomed to a fiasco.

After such an event, Weng Tonghe satirized Li Hongzhang's "Prime Minister Hefei is thinner than the world", and Li Hongzhang did not show weakness, refuting Weng Tonghe's "Si Nong Changshu is barren in the world".