In  bug 877830 , I was able to determine the bug reporter had CUPS printing by the fact that the "NA Letter" media size was shown to the user as "na_letter". The reason this happens is because ParsePaper() in printing/backend/cups_ipp_util.cc is taking "na_letter_8.5x11in" (CUPS_MEDIA_LETTER) and splitting it.

Not only does this look weird to users, but it is also likely not localized. Instead, the CUPS printing backend should be using cupsLocalizeDestMedia() / cupsLocalizeDestOption() / cupsLocalizeDestValue() to get the right strings for media sizes to show users.