As I recall the story, Bill Fries was a copywriter or an Omaha ad agency. One of their clients was the Old Home bread company in Sioux City.
Fries wrote the jingle and created a pool of commercials around it -- featuring two characters: C.W. McCall, who drove a bread truck, and Mavis, the cafe waitress.
Wisely, he retained commercial rights to the song -- which he recorded, using the C.W. McCall pseudonym...and a career was born.
I remember hearing somewhere that he turned some of these jingles into real songs after word got back from some Midwestern radio stations that listeners were actually calling the stations requesting the commercials as if they were regular radio hits!