The name Ellanor is an English feminine given name derived from the Old French name Elienor, which itself comes from the Occitan phrase alia Aenor. The name's roots trace back to the Occitan word alia, meaning "other", and the Germanic name Aenor. The earliest known spelling variations include Alienor, Alionor, Alionore, and Alianor.

Historically, the name gained widespread popularity during the Middle Ages, particularly in medieval England and parts of Europe. One of the earliest documented bearers of the name was Eleanor of Aquitaine (1122-1204), the influential Queen of France and later Queen of England. Her popularity helped establish the name throughout Western Europe.

In the 13th century, the Old French variant Elienor was introduced to England by the Plantagenets, and it gradually evolved into the modern spelling of Ellanor. Another notable historical figure with this name was Eleanora di Toledo (1522-1562), an influential Duchess of Florence during the Renaissance period.

During the 16th century, the name Ellanor appeared in several literary works, including William Shakespeare's play "King John", where he referred to the character of Eleanor, the fictitious daughter of King John. This literary reference further contributed to the name's popularity in England.

In the 17th century, Ellanor was the name of a character in John Milton's epic poem "Paradise Lost". This literary reference helped cement the name's association with literary and intellectual circles during that era.

Other notable historical figures with the name Ellanor include Ellanor Pryor (1635-1717), an English writer and translator, and Ellanor Fenn (1744-1813), an English writer and poet. Additionally, Ellanor Tomlinson (1824-1895) was an English writer and reformer who advocated for women's rights and education.