In 2374, Eelwasser was reporting excellent profits, while Slug-o-Cola was doing quite badly. While posing as Lumba, Quark told Nilva that supporting Grand Nagus Zek and allowing equal rights for females would give Slug-o-Cola an edge over Eelwasser. (DS9: "Profit and Lace")
According to Legends of the Ferengi (written by two of Star Trek: Deep Space Nine's writers, Ira Steven Behr and Robert Hewitt Wolfe), Eelwasser was discovered by two boyhood friends named Sluggo and Vorp. Sluggo tricked Vorp into drinking bog water, and was surprised when Vorp commented, "Mmm. Tastes like eel."
Wasser is German for water, and a such used as a suffix in a number of drinks (not just water types) in the language.