Dr Pepper is now as popular as Pepsi. It’s still shrouded in mystery.

Does it contain prune juice? Was there an actual doctor? And more questions about the quirky soda.

“Prune juice.” “Barbecued water.” “Elixir of the gods.” Those are just some of the phrases used to describe Dr Pepper, the un-pin-downable soda brand whose secret recipe is said to include 23 flavors. This week, we learned that the purplish-red canned beverage (see, even its label contains an enigma!) had joined Pepsi to become the nation’s second-best-selling soda, behind category-dominating Coke, according to trade publication Beverage Digest. (Dr Pepper is technically a smidgen ahead, but it’s essentially a tie.)

That news might have surprised even some of Dr Pepper’s most ardent fans, many of whom revel in the kind of weird aura that surrounds their beloved, inscrutable drink. But Pepsi’s fortunes have declined, and the good doctor’s have risen, and now each brand represents 8.3 percent of the soda market. (Coke is ahead comfortably with 19.2 percent.)

The drink’s story started in 1885 at Morrison’s Old Corner Drug Store in Waco, Tex. There, pharmacist Charles Alderton was supposedly inspired by the intermingled scent of the various fruit syrups used to flavor sodas, and so he created the blend to achieve the concoction’s now-iconic flavor.