During the Eastern Jin Dynasty, the calligrapher Wang Xizhi was exceptionally talented in his youth. Grand Commandant Xi Jian held him in high regard and wished to arrange a marriage between his daughter and Wang Xizhi.

He dispatched a messenger to Wang Dao, Wang Xizhi's uncle, to propose the marriage. Wang Dao led the messenger to the east wing of the house. There, they found only Wang Xizhi, who was casually lying on the east bed with his belly exposed, eating.

The messenger returned and reported to Xi Jian, stating that the one with the bare belly on the east bed was the suitable candidate. Xi Jian was delighted, believing that Wang Xizhi's unconstrained and natural demeanor reflected a genuine and exceptional character, making him an ideal son-in-law. This idiom later became a complimentary term for a distinguished son-in-law.