It's sour. It's briny. For some, it's nauseating. For others, a godsend.

It's the pickleback shot, an unusual combination of drinking whiskey and pickle brine that has quickly become a bartending staple. Case in point? Kelly Lewis, manager of New York City's popular Crocodile Lounge, estimates she sells at least 100 pickleback shots every week.

Pickleback loyalists may swear by it, but how did this peculiar pairing make its way into cocktail culture? On today's National Pickle Day, we hit the liquor history books to find out.

PICKLEBACK HISTORY, AS WE KNOW IT

As internet legend has it, Reggie Cunningham, a former employee of Brooklyn dive bar Bushwick Country Club, invented the shot in March 2006. He was half bartending, half nursing a hangover with McClure's pickles, when a customer challenged him to join her in doing a shot of Old Crow bourbon whiskey followed by a shot of pickle juice as a chaser. As he nostalgically tells YouTube channel Awesome Dreams, "the rest is history."

Cunningham went on to introduce the pairing to more and more customers, and the demand grew so much that he decided to charge an extra dollar per shot, just for the addition of pickle brine. After that, the mixture spread like wildfire, with bars across the world from New York to California and China to Amsterdam adding "pickleback" to their menus.

THE PICKLEBACK'S UNCLEAR ORIGIN

Neil Conway, flickr // CC BY 2.0

Sure, Cunningham may have named it the pickleback shot, but after reviewing mixed reports, it appears pickle juice as a chaser is hardly novel. In Texas, for example, pickle brine was paired with tequila well before Cunningham's discovery, according to Men’s Journal. And in Russia, pickles have long been used to follow vodka shots, according to an NPR report on traditional Russian cuisine.

Unfortunately, no true, Britannica-approved record of the pickleback's origin exists, like so many do for other popular drinks, from the Manhattan to the Gin Rickey; it's internet hearsay—and in this case, Cunningham's tale is on top.

SO, WHY PICKLES?

Not sold yet? Sure, a pickle's most common companion is a sandwich, but the salty snack and its brine have terrific taste-masking powers.

"People who don't like the taste of whiskey love taking picklebacks because they completely cut the taste, which makes the shots very easy to drink," Lewis told Mental Floss. "Plus, they add a bit of salt, which blends nicely with the smooth flavor of Jameson."

Beyond taste masking, pickle juice is also a commonly used hangover cure, with the idea being that the salty brine will replenish electrolytes and reduce cramping. In fact, after a famed NFL "pickle juice game" in 2000, during which the Philadelphia Eagles destroyed the Dallas Cowboys in 109 degree weather (with the Eagles crediting their trainer for recommending they drink the sour juice throughout the game), studies have seemed to confirm that drinks with a vinegary base like pickle juice can help reduce or relieve muscle cramping.

WAYS TO PARTAKE

While core pickleback ingredients always involve, well, pickles, each bar tends to have a signature style. For example, Lewis swears by Crocodile Lounge's mix of pickle brine and Jameson; it pairs perfectly with the bar's free savory pizza served with each drink.

For Cunningham, the "Pickleback OG," it's Old Crow and brine from McClure's pickles. And on the more daring side, rather than doing a chaser shot of pickle juice, Café Sam of Pittsburgh mixes jalapeños, homemade pickle juice, and gin together for a "hot and sour martini."

If pickles and whiskey aren't up your alley, you can still get in on the pickle-liquor movement with one of the newer adaptations, including a "beet pickleback" or—gulp!—the pickled-egg and Jägermeister shot, also known as an Eggermeister.