Another observation from the party

The more linguists drink, the worse their puns get.

Case in point:

HOD was telling us about a guy he knows who is studying secret trading languages in (I think) Papua New Guinea. Each tribe in a particular area has a different trading language, which is taught to any male members of the tribe who are to become traders. When two traders run into each other in the bush, they each use their variant of the language. If they can understand each other, then they know they must be from related tribes, hence they can trust each other, and therefore they trade. No shared secret trading language = no trade.

After telling us about this, HOD mused aloud: "It's funny how which secret language you know depends on who you are related to. I suppose you could say these are clandestine languages."