One is the giant and sea god in Greek mythology, and the other is a geological term.

The giant and sea god in Greek mythology, also the sister and wife of Ochaelus, belonged to the Titan and was an ancient divine family that once ruled the world in Greek mythology. This family was the children of Uranus, the god of the heavens, and Gaia, the goddess of the earth. They once ruled the world, but were overthrown and replaced by the Zeus family. Astronomically used to refer to Enceladus, the satellite of Saturn that is eighth farthest from Saturn.

About 250 million years ago in the Late Permian, a rift appeared on the northern edge of the southern part of Pangea (later known as Gondwana, also known as Union Land), forming an ocean. The ancient Tethyan oceanic structure opened up and formed, and the current world geological structure is based on the Tethyan structure.
Theoretical proposal
In 1893, Austrian geologist Eduard Suess proposed, based on fossil records from the Alps and Africa, the existence of a shallow inland sea between the continents of Laua and Gondwana in the past. Hughes named this prehistoric sea area the Tethys Sea, named after the Greek mythological sea god Thetis. The later proposed theory of plate tectonics overturned many of Hughes' hypotheses and changed the Tethys Sea to the Tethys Ocean. However, Hughes' concept of the Tethys Sea still had its correctness and attracted considerable attention at the time, so Hughes is still considered the discoverer of the Tethys Sea and the Tethys Ocean.
Modern Theory
About 250 million years ago during the Late Permian period, a rift appeared on the northern edge of the southern part of Pangea (later Gondwana), causing the division of the Simeria continent and the emergence of new oceans to the south of the Paleotethys Ocean.
Over the next 60 million years, the Simmeria Plate separated from Pangea and moved northward, causing the ancient Tethys Ocean to shrink towards the southeastern edge of the northern Pangea (Laurea). A new ocean, the Tethys Ocean, appeared between the southern part of Pangea and the Simeria continent (today's Türkiye, Iran, Afghanistan, Tibet, **, and Malaya), replacing the original position of the ancient Tethys Ocean.
In the Jurassic period 150 million years ago, the Simmeria continent collided and joined with the northern part of Pangea (later known as the Laua continent), forming a subduction zone called the Tethys Trench. As sea levels rise, the Tethys Ocean extends into western Europe. At the same time, Pangea split into the continents of Laua and Gondwana, and the Atlantic began to emerge. During the Jurassic and Cretaceous periods (about 100 million years ago), the Gondwana continent began to split, Africa and India departed northward, crossing the Tethys Ocean, and the Indian Ocean began to emerge. The Tethys Ocean is surrounded by land thrusters, and in the late Miocene 15 million years ago, the Tethys Ocean was reduced to the Tethys Seaway, also known as the Second Tethys Sea.
Currently, regions such as India, Indonesia, and the Indian Ocean were previously covered by the Tethys Ocean. The current Mediterranean is a remnant of the West Tethys Ocean, while the Black Sea, Caspian Sea, and Aral Sea are remnants of the Sub Tethys Sea. The bottom of the Tethys Ocean is mostly hidden beneath the continents of Simeria and Laua. Hughes and other geographers found fossils of marine organisms in the rocks of the the Himalayas. This area used to be the bottom of the Tethys Ocean until the collision between the Indian continent and the Kimeiri continent raised the bottom of the sea. There is similar evidence of the Alpine orogeny in Europe, indicating that the African plate caused the Alps.
For paleontologists, the Tethys Ocean is very important because there are many continental shelves around it, where habitats can be found in these former ones

Change process
Pre Tethys (Proterozoic Early Paleozoic), approximately 2.5 billion to 35000 years old, forming a stage;
The ancient Tethys (Late Paleozoic Early Mesozoic), approximately 35000-200 million years old, was in a stage of development and prosperity;
Neotethys (Late Mesozoic Cenozoic), approximately 200 million to 2 million years ago, is a closed stage.