this: the Greek god

In Greek mythology, Poseidon (Greek: ; Latin: Neptūnus) was the god of the sea and, as "Earth-Shaker," of earthquakes. The name of the god Nethuns in Etruscan was adopted in Latin for Neptune in Roman mythology: both were sea gods analogous to Poseidon. Linear B tablets show that Poseidon was venerated at Pylos and Thebes in pre-Olympian Bronze Age Greece, but he was integrated into the Olympian gods as the brother of Zeus and Hades.

Worship of Poseidon

Poseidon was a major civic god of several cities: in Athens, he was second only to Athena in importance; while in Corinth and many cities of Magna Graecia he was the chief god of the polis. In his benign aspect, Poseidon was seen as creating new islands and offering calm seas. When offended or ignored, he supposedly struck the ground with his trident and caused chaotic springs, earthquakes, drownings and shipwrecks. Sailors prayed to Poseidon for a safe voyage, sometimes drowning horses as a sacrifice.

According to Pausanias, Poseidon was one of the caretakers of the oracle at Delphi before Olympian Apollo took it over. Apollo and Poseidon worked closely in many realms: in colonization, for example, Delphic Apollo provided the authorization to go out and settle, while Poseidon watched over the colonists on their way, and provided the lustral water for the foundation-sacrifice. Xenophon's Anabasis describes a group of Spartan soldiers in 400-399 BCE singing to Poseidon a paean - a kind of hymn normally sung for Apollo.

Like Dionysus, who inflamed the maenads, Poseidon also caused certain forms of mental disturbance. A Hippocratic text of ca 400 BCE, On the Sacred Disease says that he was blamed for certain types of epilepsy.

Bronze Age Greece

The name seems to rather transparently stem from Greek pósis "lord, husband" with a less-transparent -don element, perhaps from dea, "goddess'. If surviving Linear B clay tablets can be trusted, the name PO-SE-DA-WO-NE ("Poseidon") occurs with greater frequency than does DI-U-JA (Zeus). A feminine variant, PO-SE-DE-IA, is also found, indicating a lost consort goddess, in effect a precursor of Amphitrite. Tablets from Pylos record sacrificial goods destined for "the Two Queens and Poseidon" and to "the Two Queens and the King". The most obvious identification for the "Two Queens" is with Demeter and Persephone, or their precursors, goddesses who were not associated with Poseidon in later periods. Poseidon is already identified as "Earth-Shaker"— E-NE-SI-DA-O-NE— in Mycenaean Knossos, a powerful attribute where earthquakes had accompanied the collapse of the Minoan palace-culture. In the heavily sea-dependent Mycenean culture, no connection between Poseidon and the sea has yet surfaced; among the Olympians it was determined by lot that he should rule over the sea (Hesiod, Theogony 456): the god preceded his realm.