The name is based on an ancient quinary material system of "five elements" which comes from earliest philosophy "YinYang" a binary theory explaining the world.
This theory believes that the world is built by "YingYang",as entia of contradictions.
For “Yin” or “Yang”, they create five status: All “Yin”, All “Yang”, “Yin” Dominance, “Yang” Dominance, “Yin” “Yang” in balance.
Depending on the dominance of each "thing", they create five elements: Wood, Metal, Fire, Water, Earth.
These five elements have mutual generation and overcoming relationship among themselves. For mutual generation order, they are: water, wood, fire, earth, and metal (and metal generates water).
For mutual overcoming order, they are: earth, water, fire, gold, wood.(and wood overcomes earth).
There is an interesting example in reality: the place where it contains metal mines always has plenty of rain (an example of mutual generation).