Most likely a combination of Nell and the popular suffix -da. Nell may be a short form of different names, including Cornelia, Danielle, Ellen, Helen, Janelle, but most likely Eleanor. Eleanor is possibly derived from the Greek word eleos, which means "mercy, compassion". The first bearer was probably Eleanor of Aquitaine. In modern times, it was popularized by Eleanor Roosevelt, the former US First Lady and wife of Franklin Roosevelt. Some sources suggest another meaning of the name - "shining light".