Chances are you’ve never heard of Cheerwine. But if you do know the name? You may well be stockpiling glass bottles of it by the case.

There’s very little middle ground with this niche-market soda pop, which was available almost exclusively in the Southeast until a few years ago, when the Internet brought it to a national audience.

And now the principal online distributor of this 94-year-old North Carolina specialty has a mystery on its hands: why, pray tell, is there a Cheerwine boom? “Sales have tripled since December,” said David Rivers, the president of KegWorks, a Buffalo-based Internet retailer of old-timey sodas and drink-related products.

Analysts say Cheerwine sells seven million cases of pop a year, but Mr. Rivers declined to reveal its sales numbers at his privately held company.

Cheerwine is thought of by the uninitiated as a mere cherry soda, but those in the know say it is more than that. For one thing, it is more highly carbonated than most soft drinks. Its most popular formulation contains pure cane sugar, which, aficionados say, imparts a more satisfying mouth-feel than the high-fructose corn syrup used in most sodas. And Cheerwine diehards insist the soda is most highly addictive “when it’s bone-chilling cold,” as Mr. Rivers said.

“Cheerwine tastes like cherry soda the way Dr Pepper tastes like pepper, or Mountain Dew tastes like dew,” said Tom Barbitta, Cheerwine’s vice president for marketing. He claims his firm — the Carolina Beverage Corporation, based in Salisbury, N.C. — is the oldest soft-drink purveyor continuously in the hands of the same owners: the Ritchie family.

Mr. Rivers has several theories about the Cheerwine sales spike, and his top suspects are Facebook and Twitter. “You have to understand that Cheerwine has a huge cult following,” he said, “and the people who love it are fanatics. One of them described it to me as ‘adult crack.’ ”

Recently KegWorks has been promoting Cheerwine heavily in social media “and on Twitter and on our own blog, and suddenly the fanatics are talking to each other, giving people who have moved away from the South the sudden realization that there is the possibility of ordering it,” he said.

For many, Mr. Barbitta said, “it connects people back to their roots, if they went to North Carolina State or Duke or Chapel Hill,” so their connection, he added, “is emotional.” Thus the power of the social-network association. Cheerwine has more than 63,000 fans on Facebook.

However, online marketers have few metrics to calibrate the effectiveness of social-media campaigns. So Mr. Rivers offers possibility No. 2: the sales surge could be “a search-engine-driven phenomenon,” Mr. Rivers said, explaining that “Google may have changed its algorithm, Cheerwine may be more searchable, and for no apparent reason there is a sudden bump in sales.”

Yet another possibility, Mr. Rivers added, is that Cheerwine has been mentioned as a brand new — but oldfangled — mixer for cocktail recipes in Imbibe magazine and other drinks publications. “But I don’t know that that would account for such explosive sales growth,” Mr. Rivers said.

Cheerwine was created in an age when carbonated soft drinks were aping alcoholic beverages. Ale became ginger ale, beer became birch beer and wine became Cheerwine, Mr. Barbitta said. The pop got its name in 1917 from the drink’s winelike ruby red color and — of course! — from “the cheer you feel when you drink it,” Mr. Barbitta said.

KegWorks has, thus far, shipped Cheerwine to far-flung sodaphiles in 50 states and six foreign countries, including Japan and Britain. Oddly, though, the company’s other niche offerings — like Blenheim Ginger Ale, Regatta Ginger Beer and Q Tonic water — have not achieved comparably explosive growth.

Cheerwine’s own trucks deliver the soda in North Carolina and South Carolina, and parts of Georgia and Virginia; it is also using the Pepsi-Cola distribution system to push into Tennessee. Cheerwine is also bottled in Maryland and Modesto, Calif., but only in recent years has it been available nationally on the Internet, from KegWorks and several competitors, and on the beverage company’s own Web site, and at Cheerwinefinder.com. The realest deal, however, is bottled in Charlotte, N.C., from soda-pop concentrate manufactured from a proprietary recipe in Salisbury.

“We call that,” Mr. Barbitta said, “our secret sauce.”