Manual:$wgMetaNamespace

Details
The name of the meta namespace, used for pages regarding the wiki itself. If set to false the value of $wgSitename is assumed. The associated talk namespace is specified by $wgMetaNamespaceTalk. An alias for this namespace is "Project".

probable bugs
Using this variable might cause critical problems when using mediawiki which have been installed in some languages like Persian. for more information you might want to see the bug report in bugzilla.