Ogham is the ancient alphabet used by the Irish and Celts. It is thought it originated in circa 4-5th century Ireland though examples are found in Wales and in England. It is a system of a 25 letter alphabet and attributed to Ogma, the God of Eloquence.

Ogham's exact origins are uncertain. It is thought it may have been adapted from a sign language used by the Fili, Anruth and Ollmah to communicate to each other covertly their thoughts, prose and mystic knowledge. The various parts of the body were indicated through this signing, including the nose, arms and legs. Current theories are that the original twenty letters are the names of the 20 trees which were sacred to the Druids (the scholarly, judicial, bardic and mystic class of society during the Celtic period). In later periods for the writing of manuscripts, Ogham had several characters added in order to represent missing letters of the alphabet which were not used in the Celtic language.

Although there are theories to indicate that Ogham was a secret and ritualistic 'language', there is no direct evidence of this fact.

Ogham was carved on stones (and perhaps wood but no artifacts have survived at present), usually on the angle of the stone, but sometimes along a vertical line. Ogham was read from bottom to top and occasionally from right to left. This again is disputed as later manuscripts have shown it was read from top to bottom and left to right.

Occasionally written as Ogam or Ogum, Ogham is pronounced 'Ahg-m' or Oh-ehm'.

Ogham was not widely used. It was primarily used by the Druidic classes and used otherwise for border marking stones, grave inscriptions or a record of an event.

Ogham was divided into 5 Aicme and each Aicme is named after its first letter. These represented a series of characters. The first Aicme (B), second (H), third (M), fourth (A) and fifth – which was added later representing those letters not found in the original Celtic language (ea (ch or k); oi (th); ui (ph); ia (p); ae (x), p and the final symbols which represented the beginning and end of a text or spaces.

The list below shows the Ogham inscription, the name, the tree it represents and the modern letter equivelant.

First Aicme

Ogham - Beith
Ogham - Luis
Ogham - Fearn
Ogham - Sail
Ogham - Nion

Beith -- Birch -- B

Luis -- Rowan -- L

Fearn -- Alder -- F

Sail -- Willow -- S

Nion -- Ash -- N

Birch Tree
Rowan Tree
Alder Tree
Willow Tree
Ash Tree

Second Aicme

Ogham - Húath
Ogham - Dair
Ogham - Tinne
Ogham - Coll
Ogham - Quert

Húath -- Hawthorne -- H

Dair -- Oak -- D

Tinne -- Holly -- T

Coll -- Hazel -- C

Quert -- Apple -- Q

Oak Tree
Hazel Tree
Apple Tree

Third Aicme

Ogham - Muin
Ogham - Gort
Ogham - nGéatal
Ogham - Straif
Ogham - Ruis

Muin -- Vine -- M

Gort -- Ivy -- G

nGéatal -- Reed/Broom -- NG

Straif -- Blackthorn -- Z (ST)

Ruis -- Elder -- R

Elder Tree

Forth Aicme

Ogham - Ailm
Ogham - Onn
Ogham - Úr
Ogham - Eadha
Ogham - Iodhadh

Ailm -- Silver Fir -- A

Onn -- Furze/Gorse -- O

Úr -- Heather -- U

Eadha -- Poplar -- E

Iodhadh -- Yew -- I

Silver Fir
Poplar Tree
Yew Tree

Fifth Aicme

Ogham - Éabhadh
Ogham - Ór
Ogham - Villeann
Ogham - Ifín
Ogham - Eamhancholl

Éabhadh -- EA (CH/K)

Ór -- OI (TH)

Villiann -- UI (IO/PH)

Ifín -- IA (P/PE)

Eamhancholl -- AE (X/XI)

Ogham - Beith
Ogham - Luis
Ogham - Fearn
Ogham - Sail
Ogham - Nion