[2] In the Greek-inspired tradition, he is a brother of Jupiter and Pluto, with whom he presides over the realms of heaven, the earthly world (including the underworld), and the seas.

[8] The lectisternium of 399 BC indicated that the Greek figures of Poseidon, Artemis, and Heracles had been introduced and worshipped in Rome as Neptune, Diana, and Hercules.

[15] Neptune was considered the legendary progenitor god of the Falisci (who called themselves Neptunia proles), joining Mars, Janus, Saturn, and Jupiter as the deific father of a Latin tribe.

The date of the festival and the construction of tree-branch shelters suggest that Neptune was a god of water sources in times of drought and heat.

Neptunalia was spent under branch huts in a woods between the Tiber and the Via Salaria, with participants drinking spring water and wine to escape the heat.

It stood near the Circus Flaminius, the Roman racetrack in the southern part of the Campus Martius, and dates back to at least 206 BC.

[35] Among modern scholars, Dumézil and his followers Bloch and Schilling centre their interpretation of Neptune on the direct, concrete, limited value and functions of water.

[37] Preller, Fowler, Petersmann and Takács attribute to the theology of Neptune broader significance as a god of universal worldly fertility, particularly relevant to agriculture and human reproduction.

They interpret Salacia as personifying lust, and Venilia as related to venia: ingratiating attraction, connected with love and the desire for reproduction.

[39] These mythical data underline the reproductive function envisaged in the figures of Neptune's paredrae, particularly that of Venilia, in childbirth and motherhood.

This connection reflects the violent and brutal nature of Poseidon the earth-shaker, the linkage of horses and springs, and the animal's psychopompous character.

On the summer Consualia (August 21) it was customary to bring horses and mules, crowned with flowers, in procession and then hold equine races in the Circus.

Tertullian (De Spectaculis V 7) wrote that according to Roman tradition, Consus was the god who advised Romulus on the abduction of the Sabines.

The etymology of Poseidon, derived from Posis (lord or husband) and De (grain or earth) may have contributed to the identification of Consus with Neptune.

The scene highlights the identities and association of Nethuns and Aplu (here identified as Uśil) as main deities of the worldly realm and the life cycle.

Thesan and Uśil-Aplu, who has been identified with Śuri (Soranus Pater, the underworld sun god) clarify the transience of earthly life.

[59] The ancient grammarian Varro derived the name from nuptus ("covering", opertio), alluding to nuptiae ("the marriage of Heaven and Earth").

[63][64] His former student, Indo-Europeanist Jaan Puhvel, theorises that the name might have meant "child (neve, nephew) of the water" as part of an Indo-European fire-in-water myth.

[65] A different etymology, grounded in the legendary history of Latium and Etruria, was proposed by the 19th-century scholars Ludwig Preller, Karl Otfried Müller and Wilhelm Deeke.

The name of the Etruscan deity Nethuns or Nethunus (NÈDVNVZ) would be an adjectival form of the toponym Nepe(t) or Nepete (present-day Nepi), near Falerii.

The district was traditionally connected to the cult of Neptune, and Messapus and Halesus (the eponymous hero of Falerii) were believed to be his sons.

Nepet might be considered a hydronymic toponym of pre-Indo-European origin from a noun meaning "damp wide valley, plain", a cognate of the proto-Greek νάπη ("wooded vale, chasm").

The root *nebh- gives the Sanskrit nābhah, Hittite nepis, Latin nubs, nebula, German Nebel, and the Slavic nebo.

[74] Müller and Deeke interpreted Neptune's theology as a divine ancestor of the Latin Faliscans: the father of Messapus and Halesus, their heroic founders.

William Warde Fowler considered Salacia the personification of the virile potency which generated a Latin people, parallel with Mars, Saturn, Janus and Jupiter.

The oldest may be a fourth-century BC carved carnelian scarab from Vulci of Nethuns kicking a rock and creating a spring (Paris: Bibliothèque Nationale, Cabinet des Medailles.

Another Etruscan artifact (Nethunus, from the Luynes collection) depicts the god causing a horse to spring from the earth with a blow of his trident.

Vaticano 1.5a) depicts Neptune with Amymone (daughter of Danaus), whom he saves from assault by a satyr and teaches the art of creating springs.