The Song:

In order for it to feel more authentic, Beck filled out his Song Reader book with fragments of songs and melodies, as well as fictional album collections and made-up song titles. "My Ozark Jacuzzi" is listed as part of a collection of manly hymns, Hymns For Him.

While most of the song titles on Hymns are made-up jokes, some are references to older sheet music/songs. I don't imagine this is a reference to an older title (I found no evidence of one). I'm not sure what it is in reference too, if an "Ozark Jacuzzi" is a thing in some way? I also saw no evidence of the phrase anywhere.