A really odd concept from TSR's D&D game. If you were of the same alignment as another character, you could were able to converse with them without anyone else understanding you. D&D also limited the range of alignments to lawful, neutral and chaotic, so there were only three of these tongues, but it still seemed very odd.

Especially when ``Lawful'', the language, was the only common tongue between your character and, say, an elf from the nearby moon.

Well, we have a real world parallel to alignment languages, known as legalese, very common among lawyers. And the underworld has their own language; 313375p34k (elite speak) can be said to be onesuch, as it is the hacker lingo, so too can be said of the language present in higher corporate circles, being contrary to human rights issues, and by extension contrary to the Charter of Rights and Freedoms... illegal.

Also, you dont need to speak "lawful" to talk with elves on the moon. I'm certainly not lawful.