Synglots
This relates to evolution of social groups via aposyndesis
by Douglas Moreman

Every social group of humans has its proper language, its synglot.

This can be taken in a very watered-down sense, being true because it can hardly not be true:
If you and I have talked with each other, the words we have used with each other and might use with each other in the future are our synglot and include references to our past conversations. In this trivial sense, even a pair of acquainted people has a synglot.

Given such a weak meaning to synglot, what might become interesting is a study of different kinds or measures of synglots. Some synglots have elements that, upon experience with them, are attention-getting and suggestive of existence of a group that has that synglot. Religions are like this. New cults of all sorts have synglots.