"Jersey lightning” is a slang name for strong applejack (originally a product of New Jersey). New Jersey has been known for its applejack since at least the 1700s.
The term “Jersey lightning” has been cited in print since at least 1843. The “Jersey Lightning Cocktail” contains applejack and vermouth.
Wiktionary: Jersey lightning
In reference to New Jersey.
Jersey lightning (uncountable)
1.(US, informal) Applejack.
Wikipedia: Applejack (beverage)
Applejack is a strong alcoholic beverage produced from apples, popular in the American colonial period.
Applejack was historically made by concentrating hard cider, either by the traditional method of freeze distillation or by true evaporative distillation. The term applejack derives from jacking, a term for freeze distillation. The modern product sold as applejack is no longer produced using this traditional process.
In New Jersey, applejack was used as currency to pay road construction crews during the colonial period. A slang expression for the beverage was Jersey Lightning.
(Historical Dictionary of American Slang)
Jersey lightning n. Esp. N.J. illicitly distilled whiskey or applejack.
1852 Hazen Five Years 23: I saw three of them empty a pint bottle of apple jack, Jersey lightning, or some other equally nauseous distillation.
1863 in Horrocks Dear Parents 29: A great many of them sell whiskey of their own make which has got the name of ‘Jersey Lightning.”
1867 in W. Goldstein Playing for Keeps 80: Numerous draughts of “Jersey lightning.”
1891 Maitland Slang Dict. 167: Jersey lightning is a variety of alleged whiskey, which kills at forty rods.
1891 Bourke Border 10: Its juice could be formulated into an alcoholic drink very acceptable to the palate, even if it threw into the shade the best record ever made by “Jersey lightning"as a stimulant.
1908 Sullivan Crim. Slang 13: Jersey lightning—Bad whiskey.
1929 Bowen Sea Slang 73: Jersey Lightning. An American sailor’s term for intoxicating liquor of a particularly potent description.
(Oxford English Dictionary)
Jersey lightning n. colloq. a strong kind of apple-jack, peach-brandy, or whisky.
1852 Alta California (San Francisco) 23 Aug. 2/5 The rumsellers dealt out Jersey lightning by the gallon.
1872 G. P. Burnham Mem. U.S. Secret Service p. vi, Jersey lightning, a peculiar New Jersey drink; ‘blue ruin’.
1970 Observer 19 Apr. 9/4 This urbane and sophisticated man came to believe that after repeal Jersey Lightning would capture the fancy of the whole country, and become a standard national drink.
8 September 1843, Richmond (VA) Whig, “Beauties of Mike Walsh,” pg. 2, col. 5:
A scientific friend of ours who was present, estimated that out of the assembly there collected, at least 1000 might be candidates for the Lunatic Asylum before the expiration of a week, from the maddening effects of the Jersey lightning.
17 May 1848, National Aegis (Worcester, MA), “Joe Dunklin’s Pony,” pg. 1, col. 5:
“Well, I’ll bet you a gallon of Mongahely agin a pint of Jersey lighning, there aint another case on record!” said Joe.
23 December 1848, Alexandria (VA) Gazette, “A Rich Bill of Lading!,” pg. 4, col. 1:
Well, three barrels contain first-rate Jersey lightning, alias New England Rum!
(Also in Chronicling America, 15 February 1849, Glasgow [MO] Weekly Times, pg. 2, col. 5—ed.)
6 October 1853, Wooster (OH) Republican, “A Turnpike and a Divorce,” pg. 1, col. 3:
...liquors in great plenty from “Jersey lightning”—which is a kind of locomotive at full speed, reduced to liquid shape—to Newark champagne.