Johanna is not a common name in the United States, however a derivative of that name is Hannah. Her maiden name was Johanna Hast while her married name was Johanna or Hanna (Hast) Nelson. I was able to locate her maiden name by searching for her son Andrew W. Nelson in an Iowa State Census Collection from 1925. That collection asked for the maiden names of mothers.
The Liddie you saw listed is the spouse of John N. Nelson and was living in the household with John Peter and Hanna at the time of the 1880 census. I have only found Luella in the 1880 census.
My aunt was a daughter of Charles Emil Nelson, so John Peter was her grandfather. He lived with her family at the end of his life. She told me that the family had six boys. She never mentioned a daughter which is why I suspect she died young, long before my aunt was born.