During the final years of the Qin Dynasty, the tyrant Second Emperor Qin imposed brutal policies, plunging the people into misery. Massive uprisings erupted across the land. Xiang Yu, a noble of the fallen Chu state, led eight thousand elite soldiers from Jiangdong to rebel against Qin, soon becoming the most formidable force. Fierce in battle, Xiang Yu swept across the north and south, invincible, crushing the main Qin army at the Battle of Julu.
When Xiang Yu's army entered the Qin capital Xianyang after the dynasty's fall, his troops burned, killed, looted, and plundered. He executed the surrendered Qin emperor Ziying, set fire to the famous Epang Palace—the towering flames raged for three months without fully dying out—then seized countless treasures and abducted local women, all to take back east for his own enjoyment.
At this moment, someone suggested to Xiang Yu, "Xianyang has extremely strategic terrain and fertile land, making it perfectly suitable to establish a capital and build your empire here."
But Xiang Yu, seeing the palaces reduced to ashes and finding nothing else to hold his interest, felt a longing for his homeland and decided to return east of the river. He declared, "When a man achieves wealth and honor, he should return to his hometown in silken robes. If he does not, it is like walking abroad in fine clothes at night—who would ever see them?"
The man who offered the plan was very displeased and told everyone, "No wonder people say the men of Chu are like monkeys wearing hats—they look dignified on the outside, but once the hat is removed, their true monkey nature is revealed. How true that is!"
When word of this reached Xiang Yu, he flew into a rage and immediately ordered his men to seize the man and throw him alive into a boiling cauldron.
Later, people used the idiom "a monkey in a hat" to mock those who, despite holding high positions and wearing fine clothes, cannot shed their vulgar and base nature.
Source: *Records of the Grand Historian*, "Biography of Xiang Yu"
Meaning of the Idiom: Later, the Chinese idiom "沐猴而冠" came to describe how those who, despite holding high positions and wearing fine clothes, cannot shed their vulgar and base nature.