Calvinism originated with the Reformation in Switzerland when Huldrych Zwingli

began preaching what would become the first form of the Reformed doctrine in Zürich in 1519.

Why did Calvinism break away from the Catholic Church?

Calvin was originally trained as a humanist lawyer. He broke from the Roman Catholic Church around 1530. After religious tensions erupted in widespread deadly violence against Protestant Christians in France, Calvin fled to Basel, Switzerland, where in 1536 he published the first edition of the Institutes.

What is Calvinism in layman's terms?

: the theological system of Calvin and his followers marked by strong emphasis on the sovereignty of God, the depravity of humankind, and the doctrine of predestination.