"Bigu", also known as Quegu, Qugu, Juegu, Juegu, Jiegu and Jiegu, originated from Fang Xian's "not eating five grains" in health preservation, that is, instead of eating five grains, he filled his stomach with drugs, food and other things, or stopped eating for a certain period of time, which was a common health preservation method of the ancients.

Pigu, often associated with persuasion, is called convincing to Pigu. Being convinced, as the name implies, is to take qi. After being influenced by Taoist thought, it is called taking essence or taking qi. This is the practice of replacing food with qi, and the method of breaking the valley with conviction is always emphasized by Taoism. Since the Han Dynasty, there has been a legend that Taoist priests were persuaded to break the valley, and there were also many imitators in previous dynasties.