For those who are unfamiliar, Norn is nonbinary, meaning their gender is not a binary gender: they are neither male nor female. You might notice that everyone in the cast refers to norn as "they" or "them" instead of "he/him" or "she/her": that's why. Nonbinary is a transgender identity, and many nonbinary people, like many binary trans people, take a name other than the one they were given at birth. In this story, where names are important to your magic, it is a person's chosen name that is their true name.
Nonbinary people and other transgender people have a long history in many cultures throughout the world, and I suggest looking into it of you've never heard of the concept before or would like to learn more.