Xie An served as prime minister under Emperor Xiaowu of the Eastern Jin Dynasty.
At that time, the Former Qin in the north was immensely powerful, constantly coveting the land south of the Yangtze River and eager to swallow it whole. The Former Qin army, led by Fu Jian, had captured Liangzhou and Yizhou, and was preparing to march further south, throwing the Eastern Jin court into panic.
Xie An sent his nephew, the renowned Eastern Jin general Xie Xuan, to lead the army in resistance. They clashed with Fu Jian's forces at the Fei River, and the Eastern Jin won a decisive victory. Xie Xuan immediately dispatched a swift horse to the capital, bearing news of the great triumph.
The messenger's horse arrived at Xie An's mansion in the capital, drenched in sweat. Xie An was playing Go with a guest; after reading the letter from the front lines, he placed it gently on his seat and continued the game without changing his expression.
The guest, concerned about the war, asked, "How is the battle going?" Xie An calmly told the guest, "The children have already defeated the enemy!"
In truth, Xie An was overjoyed! After the guests left, he hurriedly stepped over the threshold, not even noticing that the teeth of his wooden clogs had broken off. When others later learned of this, they exclaimed in surprise, "Xie An is so good at concealing his emotions! He could remain so calm!"
"Jiao" means to disguise. The idiom "Jiao Qing Zhen Wu" refers to concealing one's emotions, putting on a calm appearance to show composure.
Source: *Book of Jin*, "Biography of Xie An"
Meaning of the Idiom: Later, the Chinese idiom "矫情镇物" came to describe concealing one's emotions, putting on a calm appearance to show composure.