Sarsaparilla is an aromatic flavoring agent made from the roots of several tropical vines belonging to the Smilax genus of the lily family (Liliaceae). Once a popular tonic, sarsaparilla is now used to flavor and mask the taste of medicines. In combination with wintergreen and other flavors, it is especially used in root beer. The sarsaparilla plants (Spanish zarza, “bramble,” and parrilla, “little vine”) are native to the southern and western coasts of Mexico to Peru.

Source: Britannica