What do heavenly stems and earthly branches mean by "doing" and "supporting" respectively?

Heavenly stems and earthly branches is short for "dry branch".

Heavenly stems and earthly branches is equivalent to tree trunks and leaves. They are an interdependent and coordinated whole. In ancient China, heaven was the "master" and the earth was the "slave". The interconnection between "heaven" and "dryness" is called "heavenly dryness"; The relationship between "earth" and "branch" is called "earth branch", which together is "heavenly stems and earthly branches".

There are ten characters in Tiangan, namely A, B, C, D, E, F, G, Xin, N and D, which are collectively called "Ten Tiangan".

There are twelve characters in the earthly branches, the order of which is Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai, which are collectively called "Twelve Earthly Branches".

This interesting heavenly stems and earthly branches is said to have been invented in ancient times four or five thousand years ago.