My Great Grandfather: Johan Edvard Martinsen Hunn

My great grandparents lived on a farm named Hunn in Ostfold. My great grandmother, Helga Hunn, was easily tracible back to the 1700s. I cannot find any information on my great grandfather's side, as he obviously took the farm name and his father's first name for his last name before that. Does anyone know anything about this family or how I would go about finding out what my great grandfather's family name might have been?