Languages and aliens

FrDave at Blood of Prokopius posted about the importance of languages in his games, and this paragraph particularly resonated with me:

In LL and B/X, demi-humans begin with the ability to speak several languages. One of the interesting consequences of this in my own game is that the demi-humans have become essential for interpreting the languages of monsters who occupy the ruins. To my mind, this does a nice job of re-enforcing the alien-ness of the demi-humans. It suggests that they are closer to monsters because they can converse with them, as opposed to the human characters which do not begin the game with the same kind of linguistic ability.

I'd like to "re-enforcing the alien-ness of demi-humans," but haven't done much with it rules-wise. I'll be writing up FrDave's idea for my game.