http://phpbb.cvs.sourceforge.net/*checkout*/phpbb/phpBB2/docs/coding-guidelines.html#otherconsiderations
-> "For phpBB, the language tags are not used in their raw form and instead converted to all lower-case and have the hyphen - replaced with an underscore _ where appropiate, with some examples below:"

You like this word, don't you?

BTW: Would be nice to have an "Other" Component in this tracker...