China is called the godmother. Why do you call your recognized parents godmothers? What are the allusions?

Traditionally, in China, biological parents love their children by licking their calves. Motherly love nourishes life and contains a lot of water, while non-biological parents are "dry".

Allusion: the source of water life-biological parents are the people who give life to their children; The recognized parents didn't give life, so they did.