What is the allusion of the sentence "The black dog is white and the white dog is swollen"?

From Zhang Dayou's Snow Poem in the Tang Dynasty, the full text reads: "General on the river, the well is hidden." The yellow dog is white and the white dog is swollen. It's all slang. It's quite humorous. Later generations called this kind of poem "doggerel".

Yong Xue "There is a general river and a black hole in the well. Yellow dog is white, white dog is swollen ",a blockbuster, creating a brand-new style of doggerel, which is famous throughout the ages." This poem describes the snow scene, from full picture to close-up, from color to expression. There is not a word "snow" in the whole snow, but the shape and spirit of snow are vivid.

Zhang is just an ordinary scholar. Some people say that he is a farmer, but in short, he is a nobody. However, his poem "Ode to Snow" is a blockbuster in the eyes of future generations, creating a brand-new style of doggerel, which will last forever. Such poems are generally easy to understand, humorous and sometimes ironic.

In modern times, limerick has become a masterpiece of many people and a tool for fun and irony. Moreover, great changes have taken place in content and subject matter, which began to reflect real life and show people's thoughts, demands and wishes, with distinctive characteristics of the times, but the artistic style of limerick has not changed.