True name

Various religions and mystical traditions have a concept called a "true name," believed to be a name that is intimately connected to the essence of a thing. It is said that knowing a thing's true name grants you power over them.

Many legends speak of the existence of a Book of Names, containing the names of all beings in existence—past, present, and future.

Lucians believe Eva and Adamus were given the true names of all things.

Because giving out your true name on a business card is generally not a good idea, many entities go by aliases. For example, you know how many ultroloths are named after diseases (e.g., Anthraxus, Bubonix, Cholerix)? These are obviously not their true names. Similarly, the balor known as the Kingslayer goes by "the Kingslayer" because, again, he isn't keen on just handing out his true name willy-nilly.