Before he was C.W. McCall, the performer was a copywriter for a Chicago ad agency. One of the agency's accounts was Old Home bread, out of Sioux City, Iowa (I believe it was).
He actually wrote the "Old Home Filler-Up an' Keep on A-Truckin' Café" as a jingle for the bread company. But he retained the commercial rights to the song...
The rest is history.
He did the same for Kerns Bread in Knoxville, Tennessee. I heard the commercial version long before I heard the album version.