By knowing something’s name, true name, a magical link can be created by associating yourself to it in a magical sense, in a similar way that you would if you had hair, nail clippings, or blood. You have to know exactly how to say the name, just knowing it is not good enough.
All beings have a name and a Name. Anytime anyone says your name it touches you, but when a Wizard, or a supernatural being, says your Name, and means it, the effect is amplified a thousandfold. Names with a capital N, have power. If a wizard has an entity or persons name, they automatically have a conduit, a way to home in on it.
Your Name is valuable currency, but trading it is only for the reckless, desperate and the stupid.