"Speaking in tongues" was most probably translated from an ancient word that meant being bilingual or multilingual. I imagine some people wandered outside of their home territory and learned new languages in other areas.
This baby talk bullshit is just some more of the ear tickling lies being brought to you by those who make a good living and tidy fortune off of misrepresenting spiritual matters.
There is no demon embodied in these people except the demon of deceit. What they do is done consciously and in their own mind. They do this to appear "more spiritual" than others and just like JWs, they think this performance shows everyone else that they are "closer to god than you are". Some religions require that one has to speak in tongues as "Proof" that they have been accepted by god and have salvation. It is called "Baptism of the Holy Spirit" and yes, it is a blasphemy.