Nickname
From MIXXnet Wiki
zelrac deldarace orbocbo gettrt chirel A nickname is a name chosen by a user to identify themselves. It can be based on a real name, or completely made up. They are convenient for anonymity while still providing identification.
On MIXXnet IRC servers, you can register your nickname (also called a nick) with NickServ so that only a person with the password can use that nick.