What does it mean that my nephew cuts his hair and my uncle pays for it?

Because the nephew's haircut will damage his uncle, in order not to let his nephew shave his head, his uncle will give him lucky money.

In some local customs, if my nephew shaves his head in the first month, it will make my uncle have a bad year. So in some places, my uncle doesn't give my nephew lucky money, and my nephew takes shaving as a hint.

This is also a feudal superstition, but we still have to believe in science.