The Cornish form of this name, Jennifer, has become popular in the English-speaking world.
The popularity of the name Eleanor in England during the Middle Ages was due to the fame of Eleanor of Aquitaine, as well as two queens of the following century: Eleanor of Provence, the wife of Henry III, and Eleanor of Castile, the wife of Edward I. More recently, it was borne by first lady Eleanor Roosevelt (1884-1962), the wife of American president Franklin Roosevelt.
The spelling was later altered to Cordelia when Geoffrey's story was adapted by others, including Edmund Spenser in his poem The Faerie Queene (1590) and Shakespeare in his tragedy King Lear (1606).
In the Middle Ages this name was common in England due to the popularity of medieval tales about the Trojan War. It subsequently became rare, but was revived in the 20th century.