Q: "Hoe it down and scratch your grabble sounds like farm work, but I suspect that when the minstrel's performed it, one of them did a little dance, perhaps even imitating a chicken scratching gravel"

This one got lost in the crash and I couldn't find anything in cache so... for Q, who was sooo close and undoubtedly knew the answer all along... otra vez...

"So hoe it down..." take out the "it" and you have a "hoedown" or "a type of American folk dance or square dance in duple meter, and also the musical form associated with it." (wiki.) Aaron Copeland's is probably the widest circulated in the mainstream but Sons of the Pioneers – Wagner Hoedown was always favoritest in our house.

"... and scratch your grabble." (or gravel) is the competitive form of the dance (think Soul Train Dance Line) where southereners "bring it on" as it were.

"There's buckwheat cakes and Injun batter" is a breakfast of buckwheat pancakes and hushpuppies. Fat or fatter indeed!