During the Chu-Han War, Liu Bang joined forces with Han Xin and Peng Yue to surround Xiang Yu at Gaixia. With supplies exhausted and reinforcements cut off, Xiang Yu heard Chu songs rising from all sides and, believing the Han army had already taken his homeland, broke through the encirclement and fled south, only to take his own life at the Wu River.
After Xiang Yu's death, the various feudal lords and Liu Bang's ministers gathered to discuss making Liu Bang the emperor.
“Oh no, this won’t do,” Liu Bang said upon hearing the proposal. “Why not?” his ministers asked. “Only a worthy man can become emperor; one who speaks empty words cannot take on this great responsibility—I am not fit for it.” The ministers replied, “But you are a worthy man yourself.” Liu Bang waved his hand and said, “I come from humble origins.” “Though you were merely a village chief when you rose against the Qin, years of action have proven you can lead us to overthrow tyranny and pacify the realm.” “No, no,” Liu Bang shook his head. “Let’s discuss this another time.” “A state cannot go a single day without a ruler, or chaos will ensue. What are you afraid of? If you become emperor, we will serve you unto death,” the ministers urged. Seeing he could not refuse, Liu Bang said, “Since you all deem me suitable, then I shall accept.” So he built an altar on the north bank of the Si River, offered sacrifices to Heaven, and ascended the throne. Later, the idiom “empty words and vain talk” came to mean insincere or hollow speech.
Source: *Records of the Grand Historian*, Chapter "Annals of Gaozu"
Meaning of the Idiom: Later, the Chinese idiom "空言虚语" came to describe insincere or hollow speech.