During the Western Han Dynasty, there lived a man named Wang Ji in the capital
Wang Ji had a close friend named Gong Yu. Though they differed greatly in age, their friendship ran deep. When Gong Yu served as magistrate of Henan County, he offended a prefectural official and had to remove his official cap to apologize. He said indignantly, "Once the official cap is taken off, can it ever be put back on?"
During Emperor Xuan's reign, Wang Ji's blunt advice so irritated the emperor that he stripped him of his post.
After Emperor Yuan ascended the throne, hearing of the virtuous reputations of Wang and Gong, he summoned them back to court. Later generations thus coined the phrase, "When Wang Yang (Wang Ji) holds office, Gong Gong dusts his cap," meaning that if Wang Yang became an official, he would surely recommend Gong Yu for a position.
Su Xun also used "dusting their caps in celebration," writing in his *On Guan Zhong* about a story where a virtuous man dies and the wicked dust their caps to celebrate.
During the Spring and Autumn Period, Guan Zhong helped Duke Huan of Qi dominate the central plains and was so trusted that the duke handed all state affairs over to him. Seizing the opportunity, several sycophants curried favor with Duke Huan, among whom Shu Diao, Yi Ya, and Kai Fang became the most favored. They secretly coveted power but dared not act while Guan Zhong held the reins.
Years later, Guan Zhong collapsed from overwork
However, a month later, Xi Peng also died of illness. Duke Huan then appointed Bao Shuya as prime minister. Unable to decline, Bao Shuya set a condition: "Your Majesty must keep Yi Ya and the other two at a distance; otherwise, I will absolutely not accept the post."
Duke Huan agreed on the spot. But soon, he forgot Bao Shuya's warning and recalled the trio Yi Ya, Shu Diao, and Kai Fang. Overjoyed, they dusted off their hats and celebrated together.
Soon after, Bao Shuya fell ill and died, leaving Yiya and his two cronies to seize control of state affairs, exploiting Duke Huan's grave illness to stage a rebellion. When the duke learned of this, he covered his face with his sleeve, let out a few deep sighs, and passed away.
Later, people used the idiom "dusting hats in celebration" to describe villains congratulating each other on their impending rise to power.
Source: *Book of Han*, "Biography of Wang Ji"
Meaning of the Idiom: Later, the Chinese idiom "弹冠相庆" came to describe villains congratulating each other on their impending rise to power.