During the late Warring States period, King Nan of the Eastern Zhou dynasty was a mere puppet. Though he bore the title of Son of Heaven, he held less real power than the smallest feudal lord, ruling over only a few dozen counties—and even those were split between the Eastern Zhou Duke and the Western Zhou Duke. With no authority to speak of, he drifted between the two dukes' domains, staying a few days here and a few days there, simply passing the time.
During the Warring States period, as Qin sought to conquer the six rival states, they united against it. In 257 BC, Qin attacked Zhao, which begged Wei and Chu for aid. Lord Xinling of Wei cleverly stole the king's military seal, raised an army, and defeated Qin.
When King Kaolie of Chu heard the news, he sent an envoy to report to King Nan of Zhou, requesting that he issue an imperial decree summoning the six states to join forces and attack Qin. King Nan of Zhou, who had long resented the Qin king's bullying, readily agreed and immediately ordered Chu to rally the other feudal lords. At the same time, King Nan assembled a makeshift army of 6,000 men under the Western Duke of Zhou, preparing to march alongside the allied forces against Qin.
However, King Nan of Zhou was far too impoverished to provide supplies and pay for this 6,000-man army. So, he borrowed money from the wealthy merchants and landowners within his state, issuing promissory notes and promising to repay the loans with interest after winning the war.
After borrowing the money, King Nan of Zhou sent the Duke of Western Zhou to lead the army to Yique, where they camped and awaited reinforcements from the other states. But after three months, only Chu and Yan sent troops—some states lacked the strength, others had no will to join. The grand plan to jointly attack Qin collapsed. Though no battle was fought, every coin King Nan had borrowed was already spent.
Duke of Western Zhou withdrew his troops. The creditors, holding their bonds, came daily to the palace gates demanding repayment from King Nan of Zhou. Unable to pay, with nowhere to run or hide, the king could only take refuge atop a high terrace within the palace grounds.
Later, people named this high platform the "Debt-Escaping Terrace," and used the idiom "Debts Towering Like a Terrace" to describe being heavily in debt.
Source: *Book of Han*, "Preface to the Table of Princes and Nobles"
Meaning of the Idiom: Later, the Chinese idiom "债台高筑" came to describe being heavily in debt.