Nelly

Nelly is a familiar form used for several longer names, including Helen, Eleanor, and Cornelia, and it also has an established life as a full given name. Because those names have different histories, “light” is not a reliable universal meaning for every Nelly. The intended family connection supplies the more specific explanation.

Nellie is the closest spelling alternative. Nelly can also occur as a male nickname, as with the musician born Cornell, showing why the name should not be tied to only one longer form. Choosing it independently keeps the familiar everyday sound, while using a longer family name can preserve a particular ancestor’s full identity.