Primitive Irish
Primitive Irish or Archaic Irish (), also called Proto-Goidelic,  is the oldest known form of the Goidelic languages, and the ancestor of all languages within this family. This phase of the language is known only from fragments, mostly personal names, inscribed on stone in the Ogham alphabet in Ireland and western Great Britain between the 4th and the 6th century AD, before the advent of Old Irish. These inscriptions are referred to as Orthodox Ogham, although scholastic use of the script continued residually until the early 19th century. Written records 
Primitive Irish is the oldest recorded form of the Goidelic languages. It was written in the Ogham alphabet, the usage of which can be divided into two phases, Orthodox Ogham and Scholastic Ogham. The former represents the original Druidic tradition of memorials, whereas the latter resulted from a tradition of scholarly restoration of the writing system as part of the development of a Celtic style of Catholic art, in parallel with the use of the Latin alphabet in ordinary writing. Primitive Irish is known only from Ogham fragments, usually personal names, the earliest being dated by academics to the 4th century, although some estimates for the earliest inscriptions range between the 1st and 5th centuries. Scholars agree that the orthodox written tradition is older than the surviving inscriptions. The latest inscriptions of the orthodox tradition appear to come from the 6th century. The scholastic use of Ogham continued until the early 19th century, the last inscription being found on the tomb of Mary Dempsey at Ahenny in County Tipperary, which is written in both Irish and English. Transcribed Ogham inscriptions, which lack a letter for , 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; however, none show any sign of the influence of Christianity or Christian epigraphic tradition, suggesting they date from before 391, when Christianity became the official religion of the Roman Empire. Only about a dozen of the Irish inscriptions show any such sign. There is speculation about the orthodoxy of one inscription in Hampshire and two in Scotland, but there is no academic consensus on the matter. The majority of ogham inscriptions are memorials, consisting of the name of the deceased in the genitive case, followed by , "[the stone] of the son" (Modern Irish mic), and the name of his father, or , "[the stone] of the grandson", (Modern Irish uí) and the name of his grandfather, e.g. , "[the stone] of Dalagnos son of Dalos". Sometimes the phrase , "of the son of the tribe", is used to show tribal affiliation. Inscriptions demonstrating additional information are rare, such as , "[the stone] of the priest Ronán son of Comgán". Some inscriptions appear to be border markers. Grammar 
The brevity of most orthodox ogham inscriptions makes it difficult to analyse the archaic Irish language in depth, but it is possible to understand the basis of its phonology and the rudiments of its nominal morphology. Morphology 
Surviving Ogham inscriptions are written exclusively with nouns. It is possible to deduce some morphological features of Primitive Irish nouns from these inscriptions. With the exception of a few inscriptions in the singular dative case, two in the plural genitive case and one in the singular nominative case, most known inscriptions of nouns in orthodox Ogham are found in the singular genitive, so it is difficult to fully describe their morphology. The German philologist Sabine Ziegler, however, drawing parallels with reconstructions of the Proto-Celtic language's morphology (whose nouns are classified according to the vowels that characterize their endings), limited the archaic Irish endings of the singular genitive case to , ,  and . The first ending, , is found in words equivalent to the so-called Proto-Celtic category of *o-stem nouns. This category was also recorded in the dative case using , with an inscription possibly in the nominative case also using . , in turn, is equivalent to Proto-Celtic *i-stems and *u-stems, while  corresponds to *ā-stems. The exact function of  remains unclear. Furthermore, according to Damian McManus, Proto-Celtic nasal, dental, and velar stems also correspond to the Primitive Irish  genitive, attested in names such as, , and . Phonology 
It is possible, through comparisons with other languages, to reconstruct a phonemic inventory for the properly attested stages of the language using the names used in the scholastic tradition for each letter of the Ogham alphabet, which are recorded in the Latin alphabet in later manuscripts. Vowels 
There is a certain amount of obscurity in the vowel inventory of Primitive Irish: while the letters Ailm, Onn and Úr are recognized by modern scholars as representing ,  and  respectively, there is some difficulty in reconstructing the values of Edad and Idad. They are poorly attested, and scholars believe the distinction between them might be arbitrary, in the same way as the runes peorð and cweorð in the Anglo-Saxon alphabet, but they are transcribed as  and , respectively, and probably had the respective pronunciations of  and . There were also two diphthongs, transcribed as  and . In later stages of the language, scholastic Oghamist traditions incorporated five new letters for vowels, called forfeda (supplementary), corresponding to digraphs of the orthodox spelling, but these no longer corresponded to Primitive Irish sounds. Consonants 
The consonant inventory of Primitive Irish is reconstructed by Celticist Damian McManus as follows:

The letters Cért, Gétal and Straif, respectively transliterated as ,  (or ) and , respectively, were known by the ancient scholastic Oghamists as foilceasta (questions) due to the obsolescence of their original pronunciations: the first two,  and , had merged with plain velars in Old Irish, and the third, probably , merged with . However, evidence of the original distinction between straif and sail was still present into the Old Irish period, as the séimhiú (lenition) of  produced  for lexemes originally represented by Straif but  for lexemes originally represented by Sail. The letter Úath or hÚath (transliterated as), although not counted among the foilceasta, also presented particular difficulties due to apparently being a silent letter. It was probably pronounced as  in an early stage of Primitive Irish, disappearing before the transition to Old Irish. Consonant lenition and palatalisation, which feature heavily in later stages of the language, may already have existed in an allophonic form, i.e., they were not phonemically contrastive yet. Transition to Old Irish
Old Irish, written in the Latin alphabet, has its earliest recorded texts possibly in the late 6th century, which is the traditional date of composition for the Amra Coluim Chille, a poetic elegy to St Columba of Iona by St Dallán Forgaill, the first identifiable author in the Irish language. This work, however, survives only in heavily annotated manuscripts from a later time, in an old-fashioned form of the Irish language bearing little similarity to formal Old Irish. The first text which are widely accepted to have been written in Old Irish date from the 7th century, at the inception of a national textual tradition which was cultivated alongside that of Latin by the Catholic Church in Ireland, and which supplanted the archaic literary traditions. The radical changes that characterize the transition from Primitive Irish to Old Irish are not uncommon in the development of other languages, but appear to have occurred rapidly in the case of Irish. John T. Koch, an American Celticist, theorized that these changes coincide with the conversion of the island to Christianity and the introduction of Latin as a literary language. The Irish language would then have derogated from the formal register of the language used by druids in their ceremonies and teachings. Koch believed that with the decline of paganism and the corresponding loss of influence by the druids, the language of the Irish Christian nobility would have supplanted the ancient Primitive Irish register of the pagan priests, eclipsing it completely in the 7th century. This would give the impression of rapid linguistic development, while actually representing a shift in literature to a vernacular register which had previously been obscured by the conservative influence of the druidic language. This new phase of the language shows influence from Latin, the language having been introduced to pre-Christian Ireland, which became more pronounced following St Patrick's ministry. Features 
Primitive Irish has a morphology similar to other Indo-European languages, however it did not display the most distinctive characteristics of other phases of the language including velarized ("broad") and palatalized ("slender") consonants (such consonant alterations may have existed, but they would have been allophonic), initial mutations, some loss of inflectional endings, but not of case marking, and consonant clusters. Old Irish does carry with it these distinctive features, as well as the loss of grammatical suffixes, the introduction of the letter p through loanwords and proper names, the simplification of the inflectional system, the alteration of some short vowels through vowel harmony, and, most notably, vowel elisions which resulted in distinctive consonant clusters. This last phenomenon, especially marked in the genesis of Old Irish proper, began with an application of secondary stress to the third syllable of most words with four or more syllables, and also to the fifth syllable of words with six or more, in addition to the primary stress, which fell on the first syllable, as is typical of Celtic languages. This caused apocope of (final) syllables, syncope of stressless (internal) syllables, and the shortening of all long vowels in non-initial syllables, around 500 AD and the middle of the 6th century, respectively. This loss of vowels caused consonant clusters to develop. 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 . 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 . Old Irish filed, "poet (gen.)", appears in ogham as . In each case the development of Primitive to Old Irish shows the loss of unstressed syllables and certain consonant changes. Gradually, the grammaticalization of consonant mutations introduced a new characteristic that Irish would eventually share with all other modern Celtic languages. Old Irish phonetic conditions generated different allophonic mutations over time, and with the diachronic loss of the conditions which caused the mutations, those mutations became the only way to distinguish between different grammatical forms. Thus, the mutations became differentiated phonemes with their own morphosyntactic functions. For example, in the Primitive Irish phrase  ("of the son",  being a form of the definite article), originally pronounced , the initial  would have lenited to  due to the influence of the  ending of the preceding word. The variation in the pronunciation of the word would not have caused a difference in meaning; it would be allophonic. In a later stage of the language, the Primitive Irish word  became Old Irish in, losing the final vowel which caused the lenition. However, in the Old Irish phrase in maicc ("of the son"), the m is still lenited, so the pronunciation would be . The lenition was 'reinterpreted' as being caused by the fact that maicc follows the definite article in, a rule of morphosyntax (grammar) rather than phonology. What was originally a phonological feature of the language therefore became grammaticalized. See also 
 Irish language
 Early Irish literature
 Goidelic substrate hypothesis

Notes

References

Bibliography 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

History of the Irish language
Ancient Ireland
Irish, Primitive