evilbeej | OCD research hat on.

The preceding inscriptions are all in Latin, except for the inscription from Chamalières, which is a long (12 lines) magical text written in Gaulish inscribed on a rolled lead sheet. The second line calls for the help of Maponos (here in the accusative singular, Maponon: artiu maponon aruerriíatin (RIG L-100).

Ravenna Cosmography, British Isles

A map of it. Whee.

Welsh Mythology
Maponos surfaces in the Middle Welsh narrative, the Mabinogion, as Mabon, son of Modron, who is herself the continuation of Gaulish Matrona (“Matronly Spirit”). The theme of Maponos son of Matrona (literally, child of mother) and the development of names in the Mabinogi from Common Brythonic and Gaulish theonyms has been examined by Hamp (1999), Lambert (1979) and Meid (1991). Mabon apparently features in the tale of a newborn child taken from his mother at the age of three nights, and is explicitly named in the story of Culhwch ac Olwen.
His name lives on in Arthurian romance in the guise of Mabon, Mabuz, and Mabonagrain.

(Peter Pan!)

Irish Mythology
His counterpart in Irish mythology would seem to be Mac(c) ind Ó‘c (Hamp 1999) (“Young Son”, “Young Lad”), evidently another epithet for Angus or Oenghus, the eternally youthful spirit to be found in Newgrange called Bruigh na Bóinne, a pre-Celtic Neolithic barrow or chambered tomb. Irish mythology portrays him as the son of Dagda or Daghda, king of the Irish gods and husband of Angus ’s mother Boann, an apparent personification of the River Boyne. In Irish mythology, Youthful Spirit frequently features as a trickster god and a love god.

Ogham letters
ᚁ Beith ᚐ Ailm
ᚂ Luis ᚑ Onn
ᚃ Fearn ᚒ Úr
ᚄ Sail ᚓ Eadhadh
ᚅ Nion ᚔ Iodhadh
ᚆ Uath ᚕ Éabhadh
ᚇ Dair ᚖ Ór
ᚈ Tinne ᚗ Uilleann
ᚉ Coll ᚘ Ifín
ᚊ Ceirt ᚙ Eamhancholl
ᚋ Muin ᚚ Peith
ᚌ Gort
ᚍ nGéadal
ᚎ Straif
ᚏ Ruis