The word is believed to be derived from Greek rhein, "to flow", from Indo-European *sreu-, "flow", and would thereby mean "pourer". Many vessels considered rhyta featured a wide mouth at the top and a hole through a conical constriction at the bottom from which the fluid ran. The idea is that one scooped wine or water from a storage vessel or similar source, held it up, unstoppered the hole with one's thumb, and let the fluid run into the mouth (or onto the ground in libation) in the same way wine is drunk from a wineskin today.
Smith points out that this use is testified in classical paintings and accepts Athenaeus's etymology that it was named apo tes rhyseos, "from the flowing". Smith also categorized the name as having been a recent form (in classical times) of a vessel formerly called the keras, "horn", in the sense of a drinking horn. The word rhyton is not present in what is known of the oldest form of Greek, Mycenaean Greek, written in Linear B, but the bull's head rhyton, of which many instances survive, is mentioned in the inventory of vessels at Knossos, such as tablet 231 (K872), as ke-ra-a, shown with the bull ideogram. The word is restored as an adjective, *kera(h)a, with Mycenaean intervocalic h.
It cannot be supposed that every drinking horn or libation vessel was pierced at the bottom, especially in the prehistoric phases of the form. The scoop function would have come first. Once the holes began, however, they invited zoomorphic interpretation and plastic decor in the forms of animal heads, with the fluid pouring from the spout as a mouth: bovids, equines, cervids, and even canines.
Rhyta occur among the remains of civilizations speaking different languages and language groups in and around the Near and Middle East, such as Persia from the second millennium BCE onwards. They are often shaped like an animal head or horn and can be very ornate and compounded with precious metals and stones. In Minoan Crete, silver and gold bulls' heads with round openings for the wine (permitting wine to pour from the bull's mouth) seemed particularly common, for several have been recovered from the great palaces (Iraklion Archaeological Museum).
Not all rhyta were so valuable; many were simply decorated conical cups in ceramic.