Where did the phrase Negative Nellie originate?

Nellie was never discovered. People have said that the name Nellie was added after negative for the use of alliteration.
But other sayings like Chatty Cathy, do originate from something. Chatty Cathy, has the name Cathy because the first talking dolls name was Cathy. With a string attached to her back to pull to hear her speak, she was named "Chatty Cathy". Researchers are still looking for who or what Nellie was, but as right now, the answer is there isn't a origination.