Why did Xu Beihong name him with the word "Sad"?

The origin of the name Xu Beihong

The art master Mr. Xu Beihong was originally named Xu Shoukang. He began to read the Four Books and Five Classics with his father at the age of six, and later learned painting. After the age of seventeen, he worked as a drawing teacher in three schools in his hometown. These three schools are more than 30 miles away from his home. Due to his poor family background, he always walked to and from them and was never willing to take a boat or bus. Because his family had no money for him to study, Xu Beihong never went to a formal school, so he had no education or diploma. For this reason, he was often treated coldly.

Once, Xu Beihong went to a relative's house to have a meal. Many wealthy children were wearing silk clothes, but Xu Beihong wore a cloth. He was ridiculed by others, and from then on He was cynical and determined not to wear silk clothes. In order to make a living in society, he wanted to study in a "foreign school", but his father could not afford the money. So he went to borrow money from others, but no one looked down on him as a "poor boy". This made him feel deeply about the bleak future and the desolation of the world, and he couldn't help but feel sad like the cry of wild geese, so he changed his name to "Beihong". Since then, he has always regarded himself as a mourner, and devoted himself to painting, and finally became an art master.