Again , Google to the rescue. There was more there about the song and it's relation to slaves rejoicing over the death of their master but here is the essence :
"There has been much debate over the meaning of "Jimmy Crack Corn". To note, in the original version the lyrics read "jim crack corn". "Jim crack" has traditionally been used in reference to shoddily built items,[11] Additionally, "corn" is considered an American euphemism for "corn whiskey". Other possibilities include:
- "Gimcrack corn," cheap corn whiskey;
- That it refers to "cracking" open a jug of corn whiskey;
- That "crack-corn" is related to the (still-current) slang "cracker" for a rural Southern white.[12]
- That "crack-corn" originated from the old English term "crack," meaning gossip, and that "cracking corn" was a traditional Shenandoah expression for "sitting around chitchatting."[13]
- That the chorus refers to an overseer who, without the master, has only his bullwhip to keep the slaves in line. (This is the most popular interpretation.)
Most etymologists support the first interpretation, as the term "cracker" appears to predate "corn-cracking". Also, "whipcracker" has no historical backing.[14] This suggests that, in the chorus, the slaves may be making whiskey and celebrating."