Discussion Main / IKnowYourTrueName

Deleted the following Natter from the Planescape Torment example since it has nothing to do with the trope.

• This is all based on the game universe, as defined by the Dungeons & Dragons sourcebooks. Sigil is a city where, if enough people believe it, it exists/occurs/whatever. A strong enough will can change the world. In fact, one of the main character's memories is of an argument he entered into with an unknown man. By applying apparently credible logic (it's never shown), he proves that the man doesn't exist. The man then reveals that if he were to believe it, he'd... and then he disappears from existence. One of the endings of the game involves the main character willing himself out of existence in a similar fashion.

Is there a trope for when someone willingly gives their true name?

Aren't several of these Real Life reasons not to know someone's true name, like the A-team example of someone with an arrest warrant, rather then magical reasons?