“Naag Mani” is a mythological mysterical object told in India. It is so said that If a cobra can live 100 years, a diamond like object grows on its head. The one which attains such naag mani will have the power of transforming itself into various living beings (called “Ictha poopa dharara” / “kaama roopam”) at will. If only a human being can acquire it from that snake head, he will also become most powerful earthling. This is the story told in Indian mythology. Naag = Snake : Mani = diamond
Based on that most of the south indian girls are named “Naaga Mani”