There are roughly 400 surviving orthodox inscriptions on stone monuments throughout Ireland and western Britain, the bulk of which are in southern Munster.

[18] Since ogham inscriptions consist almost exclusively of personal names and marks possibly indicating land ownership, linguistic information that may be gleaned from the Primitive Irish period is mostly restricted to phonological developments.

[19][20] In this school of thought, it is asserted that "the alphabet was created by Irish scholars or druids for political, military or religious reasons to provide a secret means of communication in opposition to the authorities of Roman Britain.

"[21] The serious threat of invasion by the Roman Empire, which then ruled over neighbouring southern Britain, may have spurred the creation of the alphabet.

[22] Alternatively, in later centuries when the threat of invasion had receded and the Irish were themselves invading western Britain, the desire to keep communications secret from Romans or Romanised Britons would still have provided an incentive.

[23] The second main school of thought, put forward by scholars such as McManus,[24] is that ogham was invented by the first Christian communities in early Ireland, out of a desire for a unique alphabet to write short messages and inscriptions in Irish.

Later scholars are largely united in rejecting this hypothesis, however,[28] primarily because a detailed study of the letters[citation needed] shows that they were created specifically for the Primitive Irish of the early centuries AD.

[citation needed] A fourth hypothesis, proposed by the scholars Rudolf Thurneysen and Joseph Vendryes, is that the forms of the letters derive from a numerical tally-mark counting system of the time, based around the numbers five and twenty, which was then adapted into an alphabet.

[29] According to the 11th-century Lebor Gabála Érenn, the 14th-century Auraicept na n-Éces, and other Medieval Irish folklore, ogham was first invented soon after the fall of the Tower of Babel, along with the Gaelic language, by the legendary Scythian king, Fenius Farsa.

After ten years, the investigations were complete, and Fenius created in Bérla tóbaide "the selected language", taking the best of each of the confused tongues, which he called Goídelc, Goidelic, after Goídel mac Ethéoir.

He also created extensions of Goídelc, called Bérla Féne, after himself, Íarmberla, after Íar mac Nema, and others, and the Beithe-luis-nuin (the ogham) as a perfected writing system for his languages.

The order of the first five letters, BLFSN, led the scholar Macalister to propose that a link between a form of the Greek alphabet used in Northern Italy in the 6th and 5th centuries BC.

[30] The ogham alphabet originally consisted of twenty letters, divided into four groups (Irish: aicme, lit.

A letter for p is conspicuously absent, since the phoneme was lost in Proto-Celtic, and the gap was not filled in Q-Celtic, and no sign was needed before loanwords from Latin containing p appeared in Irish (e.g., Patrick).

Of the five forfeda or supplementary letters, only the first, ébad, regularly appears in inscriptions, but mostly with the value K (McManus, § 5.3, 1991), in the word koi (ᚕᚑᚔ "here").

[31] Due to their limited practical use, later ogamists turned the supplementary letters into a series of diphthongs, changing completely the values for pín and emancholl.

Of the forfeda, four are glossed by the Auraicept: The fifth letter is emancholl which means 'twin of hazel' Monumental ogham inscriptions are found in Ireland and Wales, with a few additional specimens found in southwest England (Devon and Cornwall), the Isle of Man, and Scotland, including Shetland and a single example from Silchester and another from Coventry[35] in England.

The term 'scholastic' derives from the fact that the inscriptions are believed to have been inspired by the manuscript sources, instead of being continuations of the original monument tradition.

A rare example of a Christianised (cross-inscribed) Ogham stone can be seen in St. Mary's Collegiate Church Gowran, County Kilkenny.

[38] In later centuries when ogham ceased to be used as a practical alphabet, it retained its place in the learning of Gaelic scholars and poets as the basis of grammar and the rules of poetry.

Modern New Age and Neopagan approaches to ogham largely derive from the now-discredited theories of Robert Graves in his book The White Goddess.

Graves proposed that the ogham alphabet encoded a set of beliefs originating in the Middle East in Stone Age times, concerning the ceremonies surrounding the worship of the Moon goddess in her various forms.

[42] Although his theories have been discredited and discarded by modern scholars (including Macalister himself, with whom Graves corresponded),[43] they were taken up with enthusiasm by some adherents of the neopagan movement.

While some use folklore for the meanings, Robert Graves' book The White Goddess continues to be a major influence on these methods and beliefs.