From Fedora Project Wiki

Proposal

I would like to propose naming guidelines for adding language translation packages for any package. I see few packages are not following package naming of using language code only. The reason behind proposing this guideline is to have consistency in the naming of translation packages. Another reason is for yum-langpacks which uses these package names to determine which languages are available in the current repository. The yum-langpacks langavailable command reads ending -<langcode> in rpm name and uses that to indicate that language support is available. So if some packages virtually provides <pkgname>-<langcode> that language will not be considered in langavailable command.

Package maintainers can virtually provide package names as <pkgname>-<fulllanguagename> but real package name should be <pkgname>-<langcode>

The current inconsistencies I found are for packages

kde-l10n-* uses language names and in some subpackages language aliases like British, Brazil, Farsi, LowSaxon which are not real language names.

tesseract-langpack-* uses some own defined 3 letter language codes. I reported bug to rename them but virtual provides added by its maintainer.

childsplay-alphabet_sounds_* this uses language code correctly but it should end with -<langcode> and not with _<langcode>

So the proposal is

When adding language translations, package names should end with the language code of the language.
These language codes must be valid and used from /usr/share/xml/iso-codes/iso_639_3.xml or from /usr/share/i18n/locales. 
The real package name should be <pkgname>-<langcode>.