Manual:Hooks/LanguageGetSpecialPageAliases

Note: in 1.9 and 1.10, this was misspelled LangugeGetSpecialPageAliases!

Since 1.13, you can use $wgExtensionAliasesFiles.

Details

 * $specialPageAliases : associative array of magic words synonyms
 * $lang : language code (string)