Sentence:  But the denser ambiguity springs from the three "baragouins", fantastical languages, that are interspersed among the others. Their effect is to display the arbitrariness of linguistic convention, to show that all language, when looked at from the "outside," is <WSD>"baragouin</WSD>". 
Meaning of the word marked with <WSD> tags:  Unintelligible speech; gibberish, jargon.