So why should I care if Jimmy ever gets his corn cracked or not?
I understand it is a 175 year old or so minstrel tune. The rest of the song tells a story that is open to interpretation but the refrain’s meaning has been lost to me over the intervening century.
My sister and I like to go back and forth with this.
Me: Jimmy crack corn.
Sister: I don’t care.
Me: Jimmy crack corn.
Sister: I don’t care!
Me: Jimmy. Crack. Corn.
Sister: I don’t give a fuck!
Funny. You don’t look a day over 86. 
Tom Lehrer The Folk Song Army
My teenage daughter would agree with you.
The way I interpret is that a former slave is sitting around doing nothing but getting drunk and bragging about how he got away with murdering his master. He is bragging that he no longer has to worry about his master seeing him waste time or get drunk, he can do what he wants and doesn’t care who knows it.
Take that you stupid corn!
One of my favorite Bugs Bunny cartoons has Bugs singing, I think, all the verses to this folk song. We never sang it in grade school, so this was my only exposure to it.
Okay, so while it’s open to debate exactly what “Jimmy Crack Corn” refers to, it seems clear that the song is about a slave who no longer has to work because his master has died.
Which brings up a question. I assume slaves would pass to the next of kin as part of the deceased’s estate, and Jimmy wouldn’t be able to just sit around and crack corn. But let’s just say a slave owner with no family at all were to die, whether by murder, a horseback riding accident, or natural causes. What would become of the slaves? I’m guessing they wouldn’t just be set free on a technicality.
That would depend upon the time frame and the slaves’ deposition in their late master’s will. In Virginia, this would have been illegal prior to 1782, and even then the slaves needed approval by the state legislature to be set free.
<Pinkey voice> Well I fink so, Brain, but if Jimmy cracks corn and nobody cares, why does he keep on doing it? <Pv>