As an English name, Aaron has been in use since the Protestant Reformation. This name was borne by the American politician Aaron Burr (1756-1836), notable for killing Alexander Hamilton in a duel.
This was a top-ten name in France for most of the 1940s and 50s, while in Germany it was the most popular name for several years in the 1970s and 80s. In the United States it peaked in the late 1990s and early 2000s. Famous bearers include Hans Christian Andersen (1805-1875), the Danish author of such fairy tales as The Ugly Duckling and The Emperor's New Clothes, and the French fashion designer Christian Dior (1905-1957).
As an English name it has been in use since the Middle Ages, originally in the form Clare, though the Latinate spelling Clara overtook it in the 19th century and became very popular. It declined through most of the 20th century (being eclipsed by the French form Claire in English-speaking countries), though it has since recovered somewhat.