This name has never been overly common in the Christian world, and it is considered typically Jewish. It was however borne by an 11th-century Hungarian king.
As an English name it did not become common until after the Protestant Reformation, despite a handful of early examples during the Middle Ages. It was however used earlier on the European continent, being borne by several European royals, such as the 9th-century Judith of Bavaria.
As an English Christian name, Isaac was occasionally used during the Middle Ages, though it was more common among Jews. It became more widespread after the Protestant Reformation. Famous bearers include the physicist and mathematician Isaac Newton (1643-1727) and the science-fiction writer Isaac Asimov (1920-1992).