Fardel ManorTranscribed ogham inscriptions, which lack a letter for /p/, show Primitive Irish to be similar in morphology and inflections to Gaulish, Latin, Classical Greek and Sanskrit. Many of the characteristics of modern (and medieval) Irish, such as initial mutations, distinct "broad" and "slender" consonants and consonant clusters, are not yet apparent.
More than 300 ogham inscriptions are known in Ireland, including 121 in County Kerry and 81 in County Cork, and more than 75 found outside Ireland in western Britain and the Isle of Man, including more than 40 in Wales, where Irish colonists settled in the 3rd century, and about 30 in Scotland, although some of these are in Pictish. Many of the British inscriptions are bilingual in Irish and Latin, but none show any sign of the influence of Christianity or Christian epigraphic tradition, suggesting they date before 391, when Christianity became the official religion of the Roman Empire; only about a dozen of the Irish inscriptions show any such sign.The majority of ogham inscriptions are memorials, consisting of the name of the deceased in the genitive case, followed by maqi, maqqi, "of the son" (Modern Irish mic), and the name of his father, or avi, avvi, "of the grandson", (Modern Irish uí) and the name of his grandfather: for example dalagni maqi dali, "[the stone] of Dalagnos son of Dalos". Sometimes the phrase maqqi mucoi, "of the son of the tribe", is used to show tribal affiliation. Some inscriptions appear to be border markers.[
Old Irish, written from the 6th century on, has most of the distinctive characteristics of Irish, including "broad" and "slender" consonants, initial mutations, loss of inflectional endings, and consonant clusters created by the loss of unstressed syllables, along with a number of significant vowel and consonant changes including the presence of the letter p.
As an example, a 5th-century king of Leinster, whose name is recorded in Old Irish king-lists and annals as Mac Caírthinn Uí Enechglaiss, is memorialised on an ogham stone near where he died. This gives the late Primitive Irish version of his name (in the genitive case), as maqi cairatini avi inequaglas.[4] Similarly, the Corcu Duibne, a people of County Kerry known from Old Irish sources, are memorialised on a number of stones in their territory as dovinias.[5] Old Irish filed, "poet (gen.)", appears in ogham as velitas.[6] In each case the development of Primitive to Old Irish shows the loss of unstressed syllables and certain consonant changes.
These changes, traced by historical linguistics, are not unusual in the development of languages but appear to have taken place unusually quickly in Irish. According to one theory given by John T. Koch,[4] these changes coincide with the conversion to Christianity and the introduction of Latin learning. All languages have various registers or levels of formality, the most formal of which, usually that of learning and religion, changes slowly while the most informal registers change much more quickly, but in most cases are prevented from developing into mutually unintelligible dialects by the existence of the more formal register. Koch argues that in pre-Christian Ireland the most formal register of the language would have been that used by the learned and religious class, the druids, for their ceremonies and teaching. After the conversion to Christianity the druids lost their influence, and formal Primitive Irish was replaced by the then Upper Class Irish of the nobility and Latin, the language of the new learned class, the Christian monks. The vernacular forms of Irish, i.e. the ordinary Irish spoken by the upper classes (formerly 'hidden' by the conservative influence of the formal register) came to the surface, giving the impression of having changed rapidly; a new written standard, Old Irish, established itself.