MediaWiki core has a feature whereby the setting $capitalizeAllNouns = true can be set in a LanguageXx.php file. When this is set, OutputPage attaches the capitalize-all-nouns class to the page <body> element. The only languages for which $capitalizeAllNouns = true are German and languages with German as a fallback (e.g. Alemannic).
This feature is AFAICS only used by the Monobook skin to disable lowercase transformation of tab titles for those languages, so it should be removed from core and put into the Monobook skin. It is a very obscure feature and I can't see why it would ever be required for anything else apart from this one special use case.
TODO
- Move logic to MonoBook
- Remove from core