In the United States this name steadily grew in popularity through the 1950s and 60s. It shot up the charts after the release of the 1970 movie Ryan's Daughter. Within a few years it was in the top 20 names, where it would stay for over three decades. Famous bearers include the Canadian actors Ryan Reynolds (1976-) and Ryan Gosling (1980-).
It has been used as a Christian given name in the English-speaking world since the Protestant Reformation. A famous bearer was Nathan Hale (1755-1776), an American spy executed by the British during the American Revolution.
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).
The most notable bearer of the name was Cyrus the Great, the founder of the Achaemenid Persian Empire in the 6th century BC. He is famous in the Old Testament for freeing the captive Jews and allowing them to return to Israel after his conquest of Babylon. As an English name, it first came into use among the Puritans after the Protestant Reformation.