The earliest sheet-music printings (1846-47) have "Jim crack corn!" not "Jimmy," which seems not to appear until the 1940s.

So it's no "mistake" for "gimme," as suggested above.

Cracked corn was used everywhere as chicken feed.

I can't find any instance of "to crack corn" meaning "to gossip" - outside of clever explanations of the meaning of the phrase in the song.

BTW, F. D. Benteen's 1846 tune is rather more like "In and Out the Window" than what was popularized by Burl Ives.

There was another minstrel-era tune that was rather different. Sample:

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Ddigital-music&field-keywords=south+carolina+%22blue+tail+fly%22