According to the traditional view, the origin of the names of the eight diagrams and 64 hexagrams in the Zhou Yi is the theory of image, or the theory of meaning, and there is no other explanation.The image theory holds that the eight diagrams are named after certain objects, for example, Qian hexagram represents heaven because Qian is the word of heaven in ancient times
it is named Qian; according to the theory of meaning, the image of hexagram represents the reason of things, and its meaning is taken as the name of a hexagram, such as Kun Gua stands for pure yin and Yin represents obedience
The reason why Qian and Kun hexagrams are at the top of the list of 64 hexagrams is that Qian hexagrams represent heaven and Kun hexagrams represent earth, and all things can be born when heaven and earth intersect.