I wonder whether this is related to the Somerset Steam Engine, which I have never heard attributed. I have been singing it for about 30 years.

Somerset Steam Engine

Oh, way down in Somerset or so I hear tell,
There lived a young lassie, her name it was Nell,
Oh, high, wide and handsome and just seventeen,
And she longed for a ride on my Thrashin Machine.

'Twas early one evening in the merry month of June,
When most courtin' couples were lookin' at the moon,
I said "Come to the barn, Nell, where us won''t be seen,
And I'll show you the works of my Thrashin' Machine.

All the flywheels and pistons wuz spinnin' around
When out of the cylinder came a strange sound;
I reached down below for to shut off the steam,
But the chaff had been blown from my Thrashin Machine.

'Twas nine months later, on a February morn,
The pride of its nanny, a baby was born;
And under its nappy could plainly be seen
A brand new, twin cylinder, Thrashin Machine.