乐不可支 — “To be so happy that one cannot contain oneself”

In the early Eastern Han Dynasty, Zhang Kan followed Emperor Guangwu Liu Xiu, achieving great military success in the campaign against Gongsun Shu in Sichuan. He was appointed as the Prefect of Shu Commandery and later transferred to Yuyang Commandery, where he defended against the northern Xiongnu invasion.

Zhang Kan was not only courageous and adept in warfare but also dedicated to reclaiming land for farming and constructing irrigation systems. He never sought personal wealth or luxury.

The common people sang a song praising him: 'The mulberry has no attached branches, the wheat stalks bear two ears; when Lord Zhang governs, the people are overjoyed (乐不可支).'