
I’m sorry you are puzzled. Words can have more than one meaning, and all languages evolve and change over the years. In this case, there is the literal meaning, and then there is the meaning which describes a certain type of Protestant Christian. To quote Contarini earlier in the thread,It has come to be associated with a doctrine of “secondary separation” in which there can be no cooperation with people with whom you disagree theologically, and with a highly anti-intellectual stance based on a radical doctrine of sola scriptura.
While I personally do not believe that these things are part of the fundamentals of Christianity, I believe the association with this specific type of Protestant Christianity has become the more common understanding. Again, I am sorry you are puzzled about it. That’s just a darned shame.