In some cases this name can be a short form of longer names that start with Leo, such as Leonard.
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).
Despite this potentially negative association, the name was occasionally used by Christians during the Middle Ages. In the English-speaking world both Eve and the Latin form Eva were revived in the 19th century, with the latter being more common.