Common usage:
A nickname is a shortened or familiar form of a person's proper name.
Internet chat and Usenet usage:
The term nickname refers to an alias or handle used to identify someone online, and may have little relation to their proper name.
Usage on this Wiki:
On this wiki, Real Names are preferred and the norm. A common-usage nickname may qualify as a "real name", but an alias does not.
(See Real Names Please Discussion if you want to argue about it.)
Inter Wiki usage:
Also used in inter-wiki as prefix to a wiki site - 'c2:RecentChanges' with the 'c2:' being the nickname for 'http://c2.com/cgi/wiki?'.
See original on c2.com 