In Alan Lomax's Folk Songs Of North America there is one called My Sweetheart's A Mule. It's attributed to GG Korson's Minstrels Of the Mine Patch (1927)

My sweetheart's a mule in the mines,
I drive her without any lines,
On the bumpers I sit and tobacco I spit,
All over my sweetheart's behind.

I learned it but my (ex-)wife hated it when I sang it.