Of what name is "Nellie" the diminutive?

Nellie is a diminutive of Nell.

https://nameberry.com/babyname/Nellie

It is also he diminutive of Ellen and Eleanor, and their variations.


http://www.behindthename.com/name/nellie/tree

Nellie is usually given as a diminutive form of Nell, itself derived from Eleanor, Ellen or Helen. (I named my daughter Nell, as a variant on the family's use of Eleanor in a number of names.)

According to 'Behind the Name', Nell is a "Medieval diminutive of ELEANOR, ELLEN (1) or HELEN. It may have arisen from the medieval affectionate phrase mine El, which was later reinterpreted as my Nel.

VARIANTS: Elea, Ella, Ellie, Elly, Lenore, Elle, Leanora, Lenora, Nelle, Nora, Norah
DIMINUTIVES: Nellie, Nelly"

http://www.behindthename.com/name/nell

Nellie can also be the diminutive of the male name Nelson, as in baseball hall of famer Jacob Nelson (Nellie) Fox.