This contemptuous name for a poor, white resident of the southern United States comes from a 16th century term for a braggart or liar, one who makes cracks. From Alexander Barclay’s 1509 Shyp of Folys:
Crakars and bosters with Courters auenterous.
(Crackers and boasters with Courtiers adventurous.)
It is applied specifically to southern whites as early as 1766. From a letter by Gavin Cochrane to the Earl of Dartmouth on 27 June of that year:
I should explain to your Lordship what is meant by crackers; a name they have got from being great boasters; they are a lawless set of rascalls on the frontiers of Virginia, Maryland, the Carolinas and Georgia, who often change their places of abode.1
There are a couple of commonly told false etymologies. One is that it is clipping of corncracker. To crack corn is to grind it, either for food or for distilling whiskey. From this it became associated with poor southern whites due to diet and its use in making whiskey. The trouble with this explanation is that corncracker does not appear until 1835, well after cracker is well established. From the June Western Review of that year:
There is neither wit nor meaning in the terms Hoosier, Sucker, Corncracker, and Buckeye, which have become so current.2
The other explanation is that it is a reference to the cracking of a whip, of a past as an overseer of slaves. There is no evidence to support this contention.
2OED2, corn-cracker, <http://dictionary.oed.com/cgi/entry/50050333>.
Copyright 1997-2015, by David Wilton