During the reign of Emperor Wu of the Han Dynasty, Su Wu, styled Ziqing, was a native of Duling (southeast of modern Xi'an, Shaanxi). His father and elder brothers were all Han officials. At that time, the Han court repeatedly campaigned against the Xiongnu, and both sides frequently exchanged envoys to spy on each other's intentions. Both the Han and the Xiongnu detained each other's emissaries as hostages. In 100 BCE, Su Wu was appointed as a "Palace Attendant" and ordered to lead a mission to the Xiongnu to bring back the hostages.
After completing his diplomatic mission, Su Wu should have returned to the Han Dynasty, but the Xiongnu detained him on false pretenses. The Xiongnu's Chanyu (their title for king) repeatedly threatened and tried to bribe him into surrender. When Su Wu remained unyielding, he was secretly exiled to the shores of Lake Baikal to tend sheep. The Xiongnu gave him a flock of rams, saying, "When these rams give birth to lambs, you may return to Han." This was their way of saying he would never be allowed back.
To force Su Wu to surrender, the Xiongnu often sent his former friends and acquaintances to persuade him. Once, the surrendered general Li Ling came to convince him, and Su Wu replied, "Though my father and I have achieved no great merits, our entire family has received the emperor's grace and cultivation—our positions have risen to general, our titles to marquis, and we three brothers all serve at the emperor's side."
Su Wu then added, "I have always wished to sacrifice my very liver and brains upon the ground. Now that I have the chance to give my life in service, even if I face the axe or the boiling cauldron, I would truly welcome it." In other words, he was ready to be ground to dust to repay his emperor, gladly enduring any torture for the cause of loyalty.
Li Ling, deeply moved by Su Wu's righteous words, sighed and said, "Su Wu is truly worthy of being called a great loyal minister!"
Su Wu endured extreme hardship without ever yielding, holding out for nineteen years in exile among the Xiongnu. It was not until the sixth year of the Shiyuan era (81 BCE), when the Xiongnu proposed peace with the Han Dynasty, that he was finally allowed to return home.
The idiom "liver and brain splattered on the ground" originally described a violent death. Later, it came to mean giving one's utmost loyalty, willing to make any sacrifice.
Source: *Book of Han*, "Biography of Su Wu"
Meaning of the Idiom: Later, the Chinese idiom "肝脑涂地" came to describe giving one's utmost loyalty, willing to make any sacrifice.