Although these vestiges imply a strong role in earlier times, Tethys plays virtually no part in recorded Greek literary texts, or historical records of Greek religion or cults. Walter Burkert notes the presence of Tethys in the episode of Iliad XIV that the Ancients called the "Deception of Zeus", where Hera, to mislead Zeus, says she wants to go to Oceanus, "origin of the gods" and Tethys "the mother". Burkert sees in the name a transformation of Akkadian tiamtu or tâmtu, "the sea," which is recognizable in Tiamat.
One of the few representations of Tethys that is identified securely by an accompanying inscription is the Late Antique (fourth century CE) mosaic from the flooring of a thermae at Antioch, now at Dumbarton Oaks, in Washington, D.C. In the Dumbarton Oaks mosaic, the bust of Tethys—surrounded by fishes—is rising, bare-shouldered from the waters. Against her shoulder rests a golden ship's rudder. Gray wings sprout from her forehead, as in the mosaics illustrated above and below.
Tethys has sometimes been confused with another sea goddess who became the sea-nymph Thetis, the wife of Peleus and mother of Achilles during Classical times. Some myths imply a second generation relationship between the two, a grandmother and granddaughter.
Indicative of the power exercised by Tethys, one myth relates that the prominent goddess of the Olympians, Hera, was not pleased with the placement of Callisto and Arcas in the sky, as the constellations Ursa Major and Ursa Minor, so she asked her nurse, Tethys, to help. Tethys, a marine goddess, caused the constellations forever to circle the sky and never drop below the horizon, hence explaining why they are circumpolar. Robert Graves interprets the use of the term nurse in Classical myths as identifying deities who once were goddesses of central importance in the periods before historical documentation.