The name Nan ranked 1021st in popularity for females of all ages in a sample of the 1990 US Census.
Though this name has fluctuated in use, it has been quietly present throughout the last century.
Records clearly show the development of Nan as a playful variation of Ann. One might think what's true for Nan must be true for Nancy; however, the derivation of the longer name is not so clear.
In the Middle Ages, Annis (a form of Agnes) was very popular among the English and Scots. Some scholars believe Nancy developed from this name, entirely independent of Nan.