{AuthRealm}
expert option in configure Security And Authentication
tab, =Login sub-tab.. This is used in certain password encodings, and in login templates as part of the login prompt.
%AUTHREALM%
expands to 'Enter your LoginName. (Typically First name and last name, no space, no dots, capitalized, e.g. JohnSmith, unless you chose otherwise). Visit TWikiRegistration if you do not have one.'