Li Chong was the youngest son of Li Bao, the Duke of Dunhuang during the Northern Wei Dynasty. When Li Bao died, Li Chong was still very young and was raised by his eldest brother Li Cheng, the governor of Xingyang. Li Cheng was strict with his children, and while many noble youths often harassed the common people, Li Chong and Li Cheng's eldest son Li Shao never engaged in such behavior, earning them widespread praise at the time.
Later, Li Chong was appointed as "Secretary of the Central Secretariat" by standard procedure. Because of his dignified appearance and diligent work, he gradually gained imperial favor, rising step by step to become Chief of the Secretariat and Imperial Attendant, with the noble title Duke of Longxi. Yet Li Chong only grew more humble and hardworking. What was even more admirable was that in handling court affairs, he treated relatives and enemies alike with impartial justice. When a close nephew named Yin Shisun committed a crime, Li Chong had him executed according to the law, showing no leniency. Because of his unwavering loyalty, Emperor Gaozong relied heavily on him, consulting him on everything from court rituals to legal codes. During frequent wars, whenever the emperor led campaigns, he confidently entrusted all state affairs to Li Chong. The emperor once remarked, "With Li Chong managing the court's business, I can march to war without any worries about what's behind me!"
"Gu" originally means to look back, here extended to mean caring for something out of concern. The idiom "worries from behind" refers to concerns about matters left behind or future issues during a journey or process.
Source: *Book of Wei*, "Biography of Li Chong"
Meaning of the Idiom: Later, the Chinese idiom "后顾之忧" came to describe worries from behind refers to concerns about matters left behind or future issues during a journey or process.