The ogham alphabet is often called "beth luis nion". This comes from the names of the first, second, and fifth letters of the ogham. The letters consist of one to five perpendicular or angled strokes, meeting or crossing a center line.
It is thought that Ogham was inspired by the Celtic God, "Ogma", who is the God of Eloquence and Writing.
It is also thought that Ogham corresponds to the 20 trees sacred to the druids.
A 15th century treatise on Ogham, The Book of Ballymote, states that ogham was a secret, ritualistic language. Beyond this notation, there is no conclusive evidence as to the origin or specific use of Ogham.
There are several ancient Celtic manuscripts that describe the Celtic alphabet known as Ogham, from which we have gotten most if not all of our information about the Ogham. There are thought to be over 150 different ogham alphabets.
Following are the twenty letters of the Ogham as well as the five consonants. Each group of five letters forms a section called "Aicme".
Ogham Symbol Sound/Letter Name Associated Tree
Beith - pronounced (BETH) Birch
Luis - pronounced (LWEESH) Rowan
Fearn - pronounced (FAIR-n) Alder
Sail - pronounced (SHAiLuh) Willow
Nion - (NEE-uhn) Ash
hÚath (OO-ah) Hawthorn
Duir (DOO-r) Oak
Tinne (CHIN-yuh) Holly
Coll (CULL) Hazel
Quert (KWAIRT) Apple
Muin (MUHN) vine
Gort (GORT) Ivy
nGéatal (NYEH-dl) Reed
Ruis (RWEESH) Elder
Ailm (AHL-m) Silver Fir
Onn (UHN) Furze, or Gorse
Úr (OO-r) Heather
Eadha (EH-yah) Poplar
Iodhadh (EE-yoh) Yew
Fifth Aicme (Consonants)
(ch / k) Éabhadh (EHV-uh)
oi (th) Ór (Oir)
ui (io, ph) Uilleann (Uilen)
ia (p / pe) Ifín (Iphín)
ae (x / xi) Eamhancholl (Emancholl) Phagos
The earliest known form of Irish is preserved in Ogham inscriptions which date mainly from the fourth and fifth centuries. The primary manuscript sources for information related to Ogham are The Scholars Primer (Auraicept Na nEces), Values of the Forfeda (De Duilib Feda na Forfid) and the Book of Ogham (Leber Ogam).