Qin Hui was originally a minister of the Northern Song Dynasty who was taken captive to the north along with Emperors Huizong and Qinzong, where he defected to the Jin people. Four years later, the Jin released him back to the Southern Song, and he immediately proposed a traitorous policy of negotiating peace with the Jin and dividing the country north-south. The peace-seeking Emperor Gaozong told his ministers, "Now that I have Qin Hui, I am so overjoyed I cannot sleep."
From then on, Qin Hui's career soared, rising to the position of prime minister. He said to Emperor Gaozong of Song, "If Your Majesty decides to negotiate peace with the Jin, you need only discuss this matter with me alone, and not allow other officials to interfere—then the great task can be accomplished!"
Qin Hui relentlessly recruited officials who advocated surrender while persecuting those who favored war, drawing widespread condemnation from many ministers and deep hatred from the common people.
During the Southern Song Dynasty, a Jin envoy arrived to negotiate peace terms. Relying on Jin's military might, the envoy acted arrogantly and made unreasonable demands, which were unanimously opposed by pro-war officials. However, the powerful minister Qin Hui advocated accepting them.
At the time, Fan Rugui, an imperial editor and court historian, strongly opposed negotiating peace with the Jin dynasty. After discussing with colleagues in the Imperial Secretariat, he drafted a joint petition to Emperor Gaozong rejecting the humiliating peace terms. But when the petition was ready, the others, fearing retaliation from the powerful minister Qin Hui, backed out one by one. So Fan Rugui wrote to Qin Hui alone, denouncing his treason. In the letter, he declared, "If you, Qin Hui, have not lost your mind and become utterly deranged, how could you commit such a shameful act of surrendering our nation's sovereignty? By doing this, you will be cursed for ten thousand generations, forever spat upon by your descendants!"
Later, people used "sang xin bing kuang" (literally "lost heart, sick madness") to describe someone who has lost their senses, acts recklessly, and behaves as if insane. This idiom also refers to extreme cruelty.
Source: *History of Song*, "Biography of Fan Rugui"
Meaning of the Idiom: Later, the Chinese idiom "丧心病狂" came to describe how someone has lost their senses, acts recklessly, and behaves as if insane.