The name Nancy is derived from the medieval French name Annis, which was a pet form of the ancient Germanic name Arnoald or Arnaud. The name Arnoald was composed of the elements "arn" meaning "eagle" and "wald" meaning "rule". The French variant Annis eventually evolved into the modern English name Nancy.

One of the earliest recorded instances of the name Nancy can be found in the 12th century work "Roman d'Eneas", a medieval French romance poem based on Virgil's Aeneid. In the poem, the character Annis is a young woman who falls in love with the hero Aeneas.

Nancy was a relatively popular name in medieval England and France, with some notable historical figures bearing the name. One such figure was Nancy de Lacy, born in 1262, who was a wealthy heiress and landowner in Lincolnshire, England.

In the 16th century, Nancy became a popular name among the French nobility. One notable figure was Nancy de Bourbon, born in 1505, who was a French noblewoman and member of the House of Bourbon.

During the 17th century, the name Nancy gained popularity in England and Scotland. One famous bearer of the name was Nancy Astor, born in 1879, who was the first woman to sit as a Member of Parliament in the British House of Commons.

Another well-known Nancy from history was Nancy Hanks, the mother of President Abraham Lincoln. She was born in 1784 and played a significant role in shaping the life and character of one of America's most iconic leaders.

Throughout the 18th and 19th centuries, the name Nancy remained a popular choice, with several notable figures bearing the name. These include Nancy Mitford, born in 1904, a British novelist and biographer, and Nancy Reagan, born in 1921, the wife of former US President Ronald Reagan and a prominent First Lady.