The power of Names

Names are a gift, and most people have more than one. 
First there's your original name, or the name you were given at birth, and this is what's most commonly know about other people. Original names hold power for the parent, or care giver, when sproutlings are growing, but as they become their own person it loses the power because they are in the process of developing their own name. This is why most people share their original name, as it no longer holds power over them, even if they are not yet sure what their found name is.
Then there's your found name, or the name you find for yourself, that you grow into as your find your place and role within the wider world. 
As a symbol of the life long commitment you make as part of a hand fasting ceremony you exchange the gifts of rings and names. Those commitment names are often the most precious and well guarded. They are used as a token of endearment between couples, and choosing them is a serious business as you need to really know your partner to be in order to choose a suitable name for them. 
Others take on a new name after a calamity, or as a sign of a vow. This can be done as part of a ceremony, or a private dedication to a cause. These names hold power as they are a reminder of that person's journey and trauma, a recognition that they are stronger than the circumstances, and that they continue despite everything. Using those names rededicate that person to their purpose or the memory they are upholding. 
So any power the knowledge of your name has is limited to when that name applies.  And as a person grows and takes on more names the power of each diminishes.

Now, there are names and Names.

— Fae Fair