This set phrase is derived from the complaints Ji An made to the emperor.
Ji An lived at the time of Emperor Wudi of the Western Han Dynasty (206 B.C.-A.D.24). He was respected for being upright and just and for daring to speak the truth. He did not bother about small matters in personal behavior and in being an official. He was particular about actual effects and, although he did not cause a stir, he could keep the prefecture he governed in perfect order. Because of this, the imperial court transferred him to the central government from being the perfect of the Donghai Prefecture to being a commander in charge of the appointment and dismissal of the local officials.
Once, Emperor Wudi said that he would implement the policy of benevolence and justice of Confucianism and would do good turns to the people. Emperor Wudi had hardly finished his remarks when Ji An said that there was no need for the emperor to say so. Why should the emperor bother, Ji An said, about pretending to implement the policy of benevolence and justice since he was so greedy and avaricious within himself? This choked the emperor off. The emporer suddenly changed his countenance and declared the meeting over. All the civilian and military officers at court were breathless with anxiety for fear that Ji An might bring disaster upon himself because of this. After returning. Emperor Wudu said to the people around him that Ji An was a little too rude and too straightforward.
For this reason, Ji An was never promoted againt. When he was the commander in charge of the appointment and dismissal of the local of ficials, both Gongsun Hong and Zhang Tang were low-ranking officials of little importance Later, they were promoted continuously. Gongsun Hong became the prime minister and Zhang Tang became the imperial censor. However, Ji An’s post remained the same. One day, Ji An said to Emperor Wudi that the way the emperor used his ministers was just like piling up firewood, which meant that the latecomers surpassed the old-timers. Of course, Emperor Wudi could see that Ji An was complaining. So turning to his ministers, Emperor Wudi said, “It is true that no one can stop learning You see. Ji An is making more and more indisreet remarks”
The story comes from The Historical Records. Later generations use the set phrase “the latecomers surpass the old-timers” to indicate that successors can excel the predecessors, which is quite different from the original idea when Ji An said that the latecomers surpassed the oldtimers.