During the Spring and Autumn period, Duke Zhuang of Zheng, son of Duke Wu of Zheng, bestowed food upon Ying Kaoshu, the chief guard of Ying Valley. Ying Kaoshu saved the food for his mother.

Duke Zhuang was deeply moved by this filial act, especially since he had sworn an oath with his own mother, Lady Jiang, that they would not meet again until they reached the underworld (Huangquan).

Ying Kaoshu then offered a clever suggestion: they could dig a tunnel until they reached spring water, and then meet within this underground passage. This way, they would be meeting 'under the earth,' but not in the underworld.

Duke Zhuang followed this advice, and when he finally reunited with his mother in the tunnel, he was filled with profound emotion and exclaimed, 'Qile Rongrong!' (What a joyful and harmonious scene this is!).