Nellie is the English diminutive of Eleanor, Helen, or Ellen — all from the Greek Helénē, meaning "sun's ray" or "bright."
Nellie was the 14th most popular U.S. girls' name in 1880. Nellie Bly (1864-1922), the pioneering American investigative journalist, is a famous bearer. Today Nellie is returning fast as part of the vintage revival.
Nellie does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Nellie reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.