What is the origin of Qin Ling Chu idioms?

From Ji Li Ji Zhu Beiting Fu by Chao Buzhi in Song Dynasty: "Being surrounded by physiology, I was born in Qin and died in Shu."

During the Warring States Period, two great powers in Qin Chu were opposed, and other small countries tended to Qin Chu for their own interests and security. Metaphor is capricious, uncertain or unstable.