You could probably use something like genetic tracing, if you could come up with a way of fingerprinting free text semi-reliably.

My expectation is there are probably "tell words" (i.e. not used elsewhere or for that purpose) in novel ideas, and you could likely observe these spreading over time, as the ideas carrying them did.

One of the first things groups tend to do is specialize and redefine language / create jargon.