Tricksy folk!

Your nickname is your username(s) and gamertag(s) these days, while your true name is what people call you in modern western civilization IRL. So you may call me Gadg8eer, but that's not my true name. My "god-given" true name is the one my parents gave me, while your true name should probably remain known only to you.

In the old days, before the internet, this was supposed to protect you from outsiders who might be con-men or worse trying to fake their way into gaining your and your family's trust from information gained from other outlaws.

Strangely, the mythology of "the Fae are weak to cold iron" is supposed to mean "the Fae are weak to cold steel; warfare, blades and shows of physical force", not "the Fae are weak to literal iron".