Manual:$wgExtraGenderNamespaces

Details
Same as $wgExtraNamespaces, but for namespaces with gender distinction (user space). You have to define this by yourself if you have extra namespaces which need gender distinction.

the default form for the namespace should also be set using $wgExtraNamespaces for the same index.

Example: In this example the namespace name fallbacks to the MediaWiki default, so nothing needs to be added to.