Nell, once a nickname for Helen, Ellen, or Eleanor, is a sweet old-fashioned charmer that is fashionably used today in its own right. While Nell is perfectly in tune with contemporary vintage name style, it hasn't taken off the way some of its sisters have and so maintains an air of distinction. Use Nell or Nellie as a short for any name from Eleanor to Penelope or just name her Nell.
Nell was the pet name FDR called his wife Eleanor (along with Babs), the famous Little Nell in Dickens' Old Curiosity Shop was Elinor, and the infamous mistress of Charles II, Nell Gwynne, was born Eleanor as well.
Nell was the belle of the ball in the Gay Nineties, but has been off the charts since 1956. It's currently popular in France though, ranking at Number 144.
Jodie Foster played the title character of the 1994 movie Nell, and Helena Bonham Carter and Tim Burton named their daughter Nell, keeping the family tradition of names related to Helen.