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.
As a given name, Diana has been regularly used since the Renaissance. It became more common in the English-speaking world following Walter Scott's novel Rob Roy (1817), which featured a character named Diana Vernon. It also appeared in George Meredith's novel Diana of the Crossways (1885). A notable bearer was the British royal Diana Spencer (1961-1997), the Princess of Wales.
Famous bearers include the uncrowned English queen Lady Jane Grey (1536-1554), who ruled for only nine days, British novelist Jane Austen (1775-1817), who wrote Sense and Sensibility and Pride and Prejudice, British primatologist Jane Goodall (1934-), and American actress Jane Fonda (1937-). This is also the name of the central character in Charlotte Brontë's novel Jane Eyre (1847), which tells of Jane's sad childhood and her relationship with Edward Rochester.
This was the name of two ruling queens of Portugal. It was also borne by the Habsburg queen Maria Theresa (1717-1780), whose inheritance of the domains of her father, the Holy Roman emperor Charles VI, began the War of the Austrian Succession.