See this version attributed to Leadbelly:

Chorus: Jimmy, crack corn, and I don't care.
Jimmy, crack corn, and I don't care,
Jimmy, crack corn, and I don't care,
My mastas gone away.

Rod-a, he ride him and he jumped a ditch,
He ride-a, he rode him, and the pony did pitch.
The pony, he felt a little bit shy,
'Cause he's bitten by that blue-tailed fly. (Chorus)

When I went down in Louisiana,
I stayed a little while in Texarkana.
Every once in a while, I felt a little bit shy
'Cause I was bitten by that blue-tailed fly. (Chorus)

I was on my to Shreveport, Louisiana,
Then I stopped out in Caspiana.
And I felt a little bit shy,
'Cause I was bitten by that blue-tailed fly. (Chorus)

When I was drivin' along in my car
I was stoppin' most anywhere.
Once in while I look up in the sky
'Cause I was bitten by that blue-tailed fly. (Chorus)

Once in a while I do a little bit o'dance,
And some of the people come around and says, "Will you allow me a little chance?
But every once in a while I feel a little bit shy
'Cause I was bitten by that blue-tailed fly.
(Chorus) (2x)

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Source: Leadbelly version of Jimmy Crack Corn

This site notes the following about the origin of this song:
"Credited to Daniel Emmett by Spaeth but it's likely that if he wrote it from other sources. One of the earliest publications was in a series credited to him -- but the absence of his name on the earliest copies goes far toward discrediting his authorship. The subtext for this song is that the slave in fact killed the master himself, blaming it on the blue-tail fly. This is hinted at, to varying degrees, in some versions of the song".

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There's alot of theories on what "Jimmy Crack Corn" means. Here's several theories from that same site -and notice that an anonymous poster from Mudcat Discussion Forum is mentioned:

"CRACK CORN? The Civil War song, Jimmy Cracked Corn, was one of Abe Lincoln's favorite songs! However, in the song, Jimmy wasn't really cracking corn. He was sleeping, and "cracking corn" was another term for snoring.

"Jimmy Crack Corn" was slang for "gimme cracked corn" or corn liquor. "Jimcrack o' corn and I don't care" "Jimcrack" is a measure of whiskey.

"Cracking corn" for telling jokes or tall tales: "I should explain to your Lordship what is meant by crackers; a name they have got from being great boasters; they are a lawless bunch of rascals on the frontiers of Virginia, Maryland, the Carolinas and Georgia, who often change their places of abode. G. Cochrane, 1766, in "Letters," 27 June. OED; The term comes from the Scottish-northern English word crack (crake), meaning boasting, which has been used in that sense from 1460 in print. See OED, 1971 and later eds. Georgia apparntly was first called the Cracker State in print in 1808, in "Balance," Verses by a Cracker Planter.

According to "The Cassel Dictionary of Slang" "Crack-Corn" referred to White People and originally meant the White natives of Kentucky. It was apparently a variation of "corncracker" which meant a poor white farmer and was apparently applied to the natives of Florida, Georgia, Kentucky or Tennessee possibly because of their dependance on corn or maize. Corn in the British Isles refers to wheat, oats or barley as distinct from the American meaning. (From Mudcat Discussion Forum)"

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Other websites such as The Mavens' Word of the Day indicate that "To crack corn is to break or crush it into pieces".

Are there any other theories you want to throw in the mix?