Poseidon
Poseidon is one of the twelve Olympians in ancient Greek religion and mythology, presiding over the sea, storms, earthquakes and horses. He was the protector of seafarers and the guardian of many Hellenic cities and colonies. In pre-Olympian Bronze Age Greece, Poseidon was venerated as a chief deity at Pylos and Thebes, with the cult title "earth shaker"; in the myths of isolated Arcadia, he is related to Demeter and Despoina and was venerated as a horse, and as a god of the waters. Poseidon maintained both associations among most Greeks: he was regarded as the tamer or father of horses, who, with a strike of his trident, created springs. His Roman equivalent is Neptune.
Homer and Hesiod suggest that Poseidon became lord of the sea when, following the overthrow of his father Cronus, the world was divided by lot among Cronus' three sons; Zeus was given the sky, Hades the underworld, and Poseidon the sea, with the Earth and Mount Olympus belonging to all three. In Plato's Timaeus and Critias, the legendary island of Atlantis was Poseidon's domain. In Homer's Iliad, Poseidon supports the Greeks against the Trojans during the Trojan War. In the Odyssey, during the sea-voyage from Troy back home to Ithaca, the Greek hero Odysseus provokes Poseidon's fury by blinding his son, the Cyclops Polyphemus, resulting in Poseidon punishing him with storms, causing the complete loss of his ship and numerous of his companions, and delaying his return by ten years.
Poseidon is famous for his contests with other deities for winning the patronage of the city. 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. After the fight, Poseidon sent a monstrous flood to the Attic plain to punish the Athenians for not choosing him. In similar competitions with other deities in different cities, he causes devastating floods when he loses. Poseidon is a horrifying and avenging god and must be honoured even when he is not the patron deity of the city.
Some scholars suggested that Poseidon was probably a Pelasgian god or a god of the Minyans. However it is possible that Poseidon, like Zeus, was a common god of all Greeks from the beginning.
Etymology
The earliest attested occurrence of the name, written in Linear B, is Po-se-da-o or Po-se-da-wo-ne, which correspond to Ποσειδάων and Ποσειδάϝoνος in Mycenean Greek; in Homeric Greek, it appears as Ποσιδάων ; in Aeolic, as Ποτεδάων ; in Doric, as Ποτειδάν and Ποτειδᾶς ; in Arcadic, as Ποσoιδᾱν. In inscriptions with Laconic style from Tainaron, Helos and Thuria as Ποὁιδάν, indicating that the Dorians took the name from the older population. The form Ποτειδάϝων appears in Corinth.The origins of the name "Poseidon" are unclear and the possible etymologies are contradictive among the scholars. One theory breaks it down into an element meaning "husband" or "lord" and another element meaning "earth" , Doric for γῆ ), producing something like lord or spouse of Da, i.e. of the earth; this would link him with Demeter, "Earth-mother". Burkert finds that "the second element δᾶ- remains hopelessly ambiguous" and finds a "husband of Earth" reading "quite impossible to prove". According to Beekes in Etymological Dictionary of Greek, "there is no indication that δᾶ means 'earth'", although the root da appears in the Linear B inscription E-ne-si-da-o-ne, "earth-shaker".
Another theory interprets the second element as related to the Doric word *δᾶϝον dâwon, "water", Proto-Indo-European *dah₂- "water" or *dʰenh₂- "to run, flow", Sanskrit दन् dā́-nu- "fluid, drop, dew" and names of rivers such as Danube or Don. This would make *Posei-dawōn'' into the master of waters.
Plato in his dialogue Cratylus gives two traditional etymologies: either the sea restrained Poseidon when walking as a "foot-bond", or he "knew many things".
Beekes suggests that the word has probably a Pre-Greek origin. The original form was probably the Mycenean Greek Ποτειδάϝων. "The intervocalic aspiration suggests a Pre-Greek origin rather than an Indoeuropean one".
Bronze Age Greece
Linear B (Mycenean Greek) inscriptions
If surviving Linear B clay tablets can be trusted, thenames po-se-da-wo-ne and Po-se-da-o occur with greater frequency than does di-u-ja. A feminine variant, po-se-de-ia, is also found, indicating a lost consort goddess, in effect the precursor of Amphitrite.
Poseidon was the chief god at Pylos. The title wa-na-ka appears in the inscriptions. Poseidon was identified with the title wanax from the Homeric era to classical Greece. The title didn't mean only king, but also protector. Wanax had chthonic aspects, and he was closely associated with Poseidon, who had the title "Lord of the Underworld". The chthonic nature of Poseidon is also indicated by his title E-ne-si-da-o-ne in Mycenean Knossos and Pylos. Through Homer the epithet was also used in classical Greece..
Po-tini-ja was the chief goddess at Pylos and she was closely associated with Poseidon. She was the Mycenean goddess of nature and Poseidon—Wanax is one from the gods who may be considered her "male paredros". The earth shaker received offerings in the cave of the goddess of childbirth Eileithyia at Amnisos in Crete. Poseidon is allied with Potnia and the divine child.
Wa-na-ssa appears in the inscriptions usually in plural.. The dual number is common in Indoeuropean grammar and the duality was used for Demeter and Persephone in classical Greece. Potnia and wanassa refer to identical deities or two aspects of the same deity.
E-ri-nu is attested in the inscriptions. In some ancient cults Erinys is related to Poseidon and her name is an epithet of Demeter.
It is possible that Demeter appears as Da-ma-te in a Linear B inscription, however the interpretation is still under dispute. Si-to Po-tini-ja is probably related with Demeter as goddess of grain.
Tablets from Pylos record sacrificial goods destined for "the Two ladies and the Lord". Wa-na-ssoi may be related with Demeter and Persephone, or their precursors, goddesses who were not associated with Poseidon in later periods.
Mycenean cult
During the Mycenean period, the ancestral male gods of the Myceneans were probably not represented in human forms, and the information given by the tablets found at Pylos and Knossos is insufficient. Poseidon was the chief deity at Pylos and Thebes. He is identified with Anax and he carried the title "Master of the Underworld". Anax had probably a cult associated with the protection of the palace. In Acrocorinth he was worshipped as Poseidon Anax during the Mycenean age. In the city there was the famous spring Peirene which in a myth is related to the winged horse Pegasus. In Attica there was a cult of Anax heroes who was connected to Poseidon. 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. Potnia was the Mycenean goddess of nature and she was the consort of Poseidon at Pylos. She is mentioned together with bucrania in decorated jugs and he was associated with the animals and especially to the bull. In Athens Poseidon was an inland god who created the salt-sea Erecthēιs, "sea of Erechtheus". In Acropolis his cult was superimposed on the cult of the local ancestral figure Erechtheus. In Athens and Asine he was worshipped in the house of the king during the Mycenean period. The bull was the favourite animal for sacrifices and it seems that horses were rarely used during the burial of the Mycenean leaders.Arcadian myths
In the Arcadian myths, Poseidon is related to Demeter and Despoina and he was worshipped with the surname Hippios in many Arcadian cities. At Thelpusa and Phigalia there were sister worships which are very important for the study of primitive religions. In these cults Demeter and Poseidon were chthonic divinities of the underworld.Near Thelpusa the river Ladon descended to the sunctuary of Demeter Erinys. During her wandering in search of her daughter Demeter changed into a mare to avoid Poseidon. 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. Her daughter obviously had the shape of a mare too. At first Demeter became angry and she was given the surname Erinys by the Thelpusians. The Erinyes were deities of vengeance, and Erinys had a similar function with the goddess Dike. In the very old myth of Thelpusa Demeter-Erinys and Poseidon are divinities of the underworld in a pre-mythic period. Poseidon appears as a horse. In Greek folklore the horses had chthonic associations and it was believed that they could create springs. In European folklore the water-creatures or water-spirits appear with the shape of a horse or a bull. In Greece the river god Acheloos is represented like a bull or a man-bull. Many people when sacrificed to Demeter should make a premilinary sacrifice to Acheloos
At Phigalia Demeter had a sanctuary in a cavern and she was given the surname Melaina. The goddess was related to the black undeworld. In a similar myth Poseidon appears as horse and Demeter gives birth to a daughter whose name was not allowed to be told to the unitiated. Demeter angry with Poseidon put on a black dressing and shut herself in the cavern. When the fruits of the earth were perished, Zeus sent the Moirai to Demeter who listened to them and led aside her wrath. In this cult we have traces of a very old cult of Demeter and Poseidon as deities of the underworld.
In another Arcadian myth when Rhea had given birth to Poseidon, she told Cronus that she had given birth to a horse, and gave him a foal to swallow instead of the child. In the Homeric Hymn Demeter puts a dark mourning robe around her shoulders as a sign of her sorrow. Demeter's mare-form was worshipped into historical times. The xoanon of Melaina at Phigalia shows how the local cult interpreted her, as goddess of nature. 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.