Although most of them are located in Aquileia (Friuli, Italy), the main centre of his cult, the name has also been found in places where Celtic speakers lived in ancient times, including in Gaul, Noricum, Illyria, Britain and Ireland.
[8] Alternatively, Peter Schrijver has proposed that Belenos might be an o-stem of the Indo-European root *bʰel-, designating the henbane (cf.
Welsh bela, Germanic *bel(u)nōn, Slavic *bъlnъ), a psychoactive plant which was known as belenuntia in Gaulish and as apollinaris in Latin.
[9] Bernhard Maier and Patrizia de Bernardo Stempel have also argued that the name may derive from a root *gwelH-, meaning 'source, spring'.
[5][15] The Gaulish term belenuntia (Βελενούντιαν), designating the henbane, a hallucinogenic plant also known in Latin as apollinaris, may be a derivative form of Belenos.
[8] Spanish scholarship also relates the deity's name to Aquitanian anthroponym Belinatepos or Belanetepos (taken to have an equine association), as well as the toponyms Beleño and Beloño.
[23][22][24] The god was venerated as Apollo Belenus at the curative shrine of Sainte-Sabine (Burgundy), where he was invoked by pilgrims seeking cures for their sickness.
If Belenus is interpreted as meaning 'shining, brilliant', it can be compared to the Celtic epithet Vindonnus (from *windo- 'white'), attached to Apollo as a deity who restored light and vision to people with eye disease at Essarois (Burgundy).
[22] Philologist Marjeta Šašel Kos thinks that the worship of Belenus spread from Noricum towards the nearby towns of Aquileia and Iulium Carnicum (modern Zuglio).
Inscriptions dedicated to Belenus are concentrated in the Eastern Alps and Gallia Cisalpina, but there is evidence that the popularity of the god became more widespread in the Roman period.
[22][12] During the siege of the city in 238 AD by emperor Maximinus Thrax, who died during the event while his army was defeated soon afterwards, Belenus was invoked as the divine protector of Aquileia.
[12] The soldiers reported seeing an appearance of the god floating in the air, battling and defending his town, in an evocation of Apollo's defence of Delphi against the troops of Brennos.
[27] Ausonius (later 4th century AD) alludes to sanctuaries dedicated to Belenus in Aquitania, and mentions a temple priest of the cult named Phoebicius.
[22] A votive inscription from Caesarean times by the poet Lucius Erax Bardus was found at Rochemolles, near Bardonecchia (Bardonnèche), in Italy (Alpi Graie).
[8] In Noricum, Belenus may also have been accompanied by an otherwise unknown female deity named Belestis (or Beléna, Beléstis Augústa, Beléstris, Belínca), possibly worshipped as a goddess of nature and fertility.