The commonly used term 'paradigm shift' is actually a fairly recent concept, one that dates back to the 1962 publication of Thomas Kuhn’s book The Structure of Scientific Revolutions.
The book itself represented a paradigm shift.
Kuhn was exploring the evolution of our scientific understanding. He found that there were moments in time when new experiences forced radically new models.
Existing models of understanding would incrementally evolve until new experiences began to emerge that didn’t fit. A tension between the old model and new experiences would continue until a radical restructuring of the model appeared that integrated these new experiences.
A struggle between adherents of the old and new models would then erupt, until there was a Tipping Point and the new model became the dominant one.