This name was borne by a number of important saints, including Cyril of Jerusalem, a 4th-century bishop and Doctor of the Church, and Cyril of Alexandria, a 5th-century theologian. Another Saint Cyril was a 9th-century Greek missionary to the Slavs, who is credited with creating the Glagolitic alphabet with his brother Methodius in order to translate the Bible into Slavic. The Cyrillic alphabet, named after him, is descended from Glagolitic.
This name has been especially well-used in Eastern Europe and other places where Orthodox Christianity is prevalent. It came into general use in England in the 19th century.
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.
It has never been very common as a given name in the English-speaking world, though it rose in popularity after the middle of the 20th century. In the United States it is frequently an African-American name. In Lithuania it may be given in honour of the Lithuanian-American aviator Steponas Darius (1896-1933), who died attempting to fly nonstop from New York to Lithuania. His surname was an Americanized form of the original Darašius.
This name was popular throughout the English-speaking world in the early 20th century. It staged a comeback in the early 21st century, returning to the American top ten in 2017.