The word "bosom friend" comes from the story of Yu Boya and Zhong Ziqi (said to be people in the Spring and Autumn Period). According to legend, Yu Boya is good at playing drums and Zhong Ziqi is good at listening to the piano. Every time Boya thinks of something, Zhong Ziqi can understand what Boya is thinking from the sound of the piano.
After the hippo chef died, Boya broke his beloved piano and broke the strings. He never played again, because he had no confidant and no one knew him better. The friendship between two "bosom friends" touched future generations, and people often use bosom friends to describe the friendship between friends.
Since Liezi and Lu Chunqiu, the ancient books of the Western Han Dynasty, such as Biography of Korean Poetry, Huainanzi, Shuoyuan, Tongzhi of Customs, Cao Qin, and Yuefu Jie of Eastern Han Dynasty, have been quoted one after another. In these works, the description of Boya is more abundant. For example, Cai Yi's Cao Qin in the Eastern Han Dynasty also recorded an anecdote about Boya learning the method of empathy from musicians.
In Ming Dynasty, Feng Menglong's "Words of Warning to the World" started with "Yu Boya practicing the piano to thank his companions". In this novel, Boya becomes Yu Boya, a music official, and Zhong Ziqi becomes a woodcutter in Hanyang. An ancient small dictionary has completely turned into a novel, with characters, places and plots.