During the early Eastern Han Dynasty, Ma Yuan, a celebrated general under Emperor Guangwu of Han, earned the titles of General of the Waves and Marquis of Xinxi for his outstanding military achievements, winning the emperor's deep trust.
In 40 AD, the general Ma Yuan was ordered by Emperor Liu Xiu to lead a campaign against Jiaozhi (modern-day northern Hanoi, Vietnam). Though a remote and wild region, Jiaozhi produced a plant called coix, whose fruit—known as coix seed or "medicine corn"—was said to strengthen the body and ward off miasma. To protect his troops from the region's deadly vapors, Ma Yuan regularly consumed coix seed. Source: *Book of the Later Han*, "Biography of Ma Yuan".
When General Ma Yuan pacified Jiaozhi, he noticed the local coix seeds were unusually large and rare in the north, so he loaded a cartful to bring back for planting.
When General Ma Yuan returned to the capital, people saw him hauling a cartload of goods and assumed it was filled with rare southern pearls and rhinoceros horns, sparking gossip among the court officials—but since Ma Yuan was then favored by Emperor Guangwu of Han, no one dared report their suspicions to the throne.
Due to the toxic miasma, many of General Ma Yuan's soldiers perished on the campaign, and Ma Yuan himself fell gravely ill upon returning to the capital. One day, Emperor Guangwu's son-in-law, the imperial attendant Liang Song, came to visit and performed a deep bow, but Ma Yuan did not rise to return the courtesy.
After Liang Song left, Ma Yuan's son said to him, "Father, Liang Song is the emperor's son-in-law, with immense power and influence—no one in the court dares not fear him. Why didn't you stand up to return his greeting?" Ma Yuan replied, "I am an old friend of his father and his elder. Though he is the emperor's son-in-law, he cannot disregard seniority!"
Years later, Ma Yuan was ordered to campaign against the barbarians in Yuxi, where he tragically contracted malaria and died in the army. At that time, Liang Song, serving as the imperial commissioner overseeing the troops, still harbored a grudge from his earlier visit to Ma Yuan's residence when Ma Yuan had not risen to greet him. So Liang Song conspired with Dou Gu, the imperial attendant, to submit a false report to Emperor Guangwu, accusing Ma Yuan of bringing back a cartload of pearls and rhinoceros horns from his previous campaign in Jiaozhi and concealing them without reporting—a grave offense.
Then the Marquis of Yangxu, Ma Wu, and the Marquis of Yuling, Hou Yu, reported to Emperor Guangwu that Ma Yuan had indeed brought back a cartload of bright pearls from Jiaozhi. Furious, the emperor ordered the recall of Ma Yuan's seal as Marquis of Xinxi.
Ma Yuan's wife and children, unaware of what exactly had incurred Emperor Guangwu's wrath, dared not bury his coffin in the family cemetery; instead, they purchased a plot of land west of Luoyang and hastily interred him there.
Ma Yuan's wife, sons, and nephews bound themselves with ropes and went to the palace to plead for forgiveness before Emperor Guangwu, begging him to explain what crime Ma Yuan had committed.
Emperor Guangwu said, "Someone reported that Ma Yuan brought back a cart of pearls from Jiaozhi and concealed them without reporting. I only ordered the confiscation of his Marquis of Xinxi seal—the punishment was already lenient!"
Ma Yuan's wife tearfully pleaded before the emperor, "Your Majesty, my husband has always been utterly loyal—how could he possibly be guilty of such a crime? Years ago, when he returned from Jiaozhi, he did bring back a cartload of goods, but it was nothing more than the seeds of coix lacryma-jobi. The seeds from Jiaozhi are large, white, and glossy, resembling pearls. If you doubt me, Your Majesty, there are still plenty of these seeds at home to prove it."
Only after hearing this did Emperor Guangwu realize he had wronged Ma Yuan, and he rescinded his previous decree, finally allowing Ma Yuan's coffin to be moved to the ancestral burial grounds.
Later, the idiom "Coix Pearl" came to describe an innocent person being suspected, slandered, and wrongfully accused.
Source: *Book of the Later Han*, "Biography of Ma Yuan"
Meaning of the Idiom: Later, the Chinese idiom "薏苡明珠" came to describe an innocent person being suspected, slandered, and wrongfully accused.