By giving out your name, you are giving them the ability to take your soul. By giving out your birthday, you have given over the control of your whole life. ~Yuuko Ichihara, xxxholic, ch1 p16
In stories where the supernatural rules, including our childhood fairy tales, names appear to yield a special power. In Natsume Yuujinchou the names of the spirits ,which she won in fun games, were written down on a paper and collected in a book by Reiko and this gave her the ability to control them. Thus, since Natsume appears again in the region the spirits try either to steal this powerful book or have their names back. The significance of a name is stressed again in a later episode in the second season where a girl, Saki, saw a malevolent spirit by accident and in order not to be eaten she should find it again within a year’s time. In the meantime, the last 13 people ,whose names she would utter, they would share the same fate as her. It’s also very common that some shounen or mahou shoujo heroes/-ines before lounching their special attack, they would say out loud its name.
It seems that this power stems from the fact that name gives an individual an identity or defines this identity as unique. Name also signifies an emotional bond. That’s why we name our pets, that’s why we call our loved one somehow else than the rest of the people. Ierarchy is also defined by names, e.g. the surname of women is in many countries the surname of their father or their husband and that is a remnant of the strong patriarchy which demanded women to submit to men as lower in compare to them.
If you have something to add, I’d be glad to hear. I’m open to other interpretations as well.