According to legend, Athena became the patron goddess of the city of Athens after a competition with Poseidon, though he remained on the Acropolis in the form of his surrogate, Erechtheus.

[13] The earliest attested occurrence of the name, written in Linear B, is 𐀡𐀮𐀅𐀃 Po-se-da-o or 𐀡𐀮𐀅𐀺𐀚 Po-se-da-wo-ne,[14] which correspond to Ποσειδάων (Poseidaōn) and Ποσειδάϝoνος (Poseidawοnos) in Mycenean Greek; in Homeric Greek, it appears as Ποσιδάων (Posidaōn); in Aeolic, as Ποτε(ι)δάων (Pote(i)daōn); in Doric, as Ποτειδάν (Poteidan) and Ποτειδᾶς (Poteidas); in Arcadic, as Ποσoιδᾱν (Posoidan).

In inscriptions with Laconic style from Tainaron, Helos and Thuria as Ποὁιδάν (Pohoidan), indicating that the Dorians took the name from the older population.

[2] According to Beekes in Etymological Dictionary of Greek, "there is no indication that δᾶ means 'earth'",[18] although the root da appears in the Linear B inscription E-ne-si-da-o-ne, "earth-shaker".

[23] If surviving Linear B clay tablets can be trusted, the names po-se-da-wo-ne and Po-se-da-o ("Poseidon")[14] occur with greater frequency than does di-u-ja ("Zeus").

The dual number is common in Indoeuropean grammar (usually for chthonic deities like the Erinyes) and the duality was used for Demeter and Persephone in classical Greece (the double named goddesses).

[34] A cult title of Poseidon was "earth-shaker" and in Knossos he was worshipped together with the goddess Eleithyia who was related to the annual birth of the divine child.

Poseidon took the form of a stallion and after their mating she gave birth to a daughter whose name was not allowed to be told to the unitiated and a horse called Arion (very swift).

A Medusa type with a horse's head with snaky hair, holding a dove and a dolphin, probably representing her power over air and water.

[45] In the heavily sea-dependent Mycenaean culture, there is not sufficient evidence that Poseidon was connected with the sea; it is unclear whether "Posedeia" was a sea-goddess.

[46] In the primitive Boeotian and Arcadian myths Poseidon, the god of the underworld, appears as a horse and he is mating with the earth goddess.

[40] The earth goddess is called Erinys or Demeter and she gives birth to the fabulous horse Arion and the unnamed daughter Despoina, which is another name of Persephone.

The Greeks believed that the cause of the earthquakes was the erosion of the rocks by the waters, by the rivers in Peloponnese which they saw to disappear into the earth and then to burst out again.

[11] The significance of his cult is indicated by the names of cities like Poteidaia in the Chalkidiki peninsula and Poseidonia (Paestum), a Greek colony in Italy.

[2] He was worshipped as "ruler of the springs" and "leader of the nymphs" [64] In Thessaly it was believed that he drained the area cutting the rocks of Tempe with his trident.

[11][70] Xenophon's Anabasis describes a group of Spartan soldiers in 400–399 BC singing to Poseidon a paean—a kind of hymn normally sung for Apollo.

[82] Some of the epithets (or adjectives) applied to him like Enosigaios (Ἐνοσίγαιος), Enosichthon (Ἐνοσίχθων) (Homer) and Ennosidas (Ἐννοσίδας) (Pindar), mean "earth shaker".

He had the epithets Krenouchos (Κρηνούχος), "ruling over springs",[122] and nymphagetes (Νυμφαγέτης) "leader of the nymphs" [123] On the Acropolis of Athens he created the saltspring Sea of Erechtheus (Ἐρεχθηίς θάλασσα).

Other epithets of Poseidon in local cults are Epoptes (Ἐπόπτης), "overseer, watcher" at Megalopolis,[131] Empylios (Ἐμπύλιος), "at the gate " at Thebes,[132] Kronios (Κρόνιος)[133] (Pindar) and semnos (σεμνός), "august, holy"[134] (Sophocles).

The five children emerged from their father's belly in reverse order, making Poseidon both the second youngest child and the second oldest at the same time.

Armed with a trident forged for him by the Cyclopes, Poseidon with his siblings and other divine allies defeated the Titans and became rulers in their place.

[170] In a rarer - and later- version, Poseidon avoided being devoured by his father as his mother Rhea saved him in the same manner she did Zeus, by offering Cronus a foal instead, claiming she had given birth to a horse instead of a god, while she had actually laid the child in a flock.

[173] In another tale, Rhea gave Poseidon to the Telchines, ancient inhabitants of the island of Rhodes;[174] Capheira, an Oceanid nymph, became the young god's nurse.

Poseidon struck the ground with his trident and a spring sprang up; the water was salty and not very useful, whereas Athena offered them an olive tree.

The depression made by Poseidon's trident and filled with salt water was surrounded by the northern hall of the Erechtheum, remaining open to the air.

[188] Poseidon and Apollo, having offended Zeus by their rebellion in Hera's scheme, were temporarily stripped of their divine authority and sent to serve King Laomedon of Troy.

[193] Poseidon, enraged, caused Minos's wife, Pasiphae, to fall in love with the bull; their coupling produced the Minotaur, a half-bull half-human creature who fed on human flesh.

[204] The philosopher Plato was held by his fellow ancient Greeks to have traced his descent to the sea-God Poseidon through his father Ariston and his mythic predecessors the demigod kings Codrus and Melanthus.

One day, Poseidon, filled with lust for Tyro, disguised himself as Enipeus, and from their union were born the heroes Pelias and Neleus, twin boys.

Odysseus is even told, notwithstanding his ultimate safe return, that to placate the wrath of Poseidon will require one more voyage on his part.