Wayne T. Carroll wrote the first published (fictional) stories about Feboldson in the 1920s. He had felt that the Gothenburg area, settled by Swedish immigrants, needed a native folklore and so he invented one. His stories were then further embellished and popularised by Paul R. Beath.
From: “The Febold Feboldson Legend,” Nebraska History 33 (1952) by Robert F Chamberlain: