A similar change occurred in British in which only stressed I and us were lowered and the lowering was caused by original long a and by the final -- a in Latin loanwords. This change is not Common Insular Celtic because it postdates raising in Goidelic and raising is not Common Insular Celtic sound change." (Tristram, 2007, p.100)
Tristram writes that in Goidelic "syncope is a completely regular process" which impacts every second syllable of a polysyllabic word, counting the last syllable (following the syncope). And in all likelihood occurring at the last of the Ogam period in the middle of the 6th century. Paraphrased) Stated to be a common morphological innovation "was the creation of conjugated prepositions or preposition nouns from earlier prepositions which were followed by inflected forms of pronouns both in British and Goidelic languages and personal pronouns merged with prepositions into "conjugated prepositions." (2007, p.101) the a preposition governs pronominal dependents it is conjugated for person but the forms of conjugated prepositions are stated to be different in British and Goidelic and this is true "even if the prepositions themselves are etymologically cognate." (Tristram, 2007, p.101)
Tristram holds that conjugated prepositions "must have been created at the time when personal pronouns were still fully inflected in Goidelic and British" which subsequently cause the loss of the inflection in this word-class "in both branches" which in British extended to "all pronouns, nouns and adjectives." (2007, p.102)
V. Common Special Imperfect Tense Shared by British and Goidelic
Tristram (2007) writes that there is a shared special imperfect tense in both British and Goidelic and that no traces of this are found in the Continental Celtic languages to date. There are however, some divergences stated in the "use of the imperfect in the two branches" leaving little doubt "that the parallels in the formation and use of the imperfect in British and Goidelic are accidental.' (p. 102)
However, Tristram states that the majority of the endings of the imperfect are non-related in British and Goidelic etymologically "so the Proto-Insular Celtic imperfect cannot be reconstructed" which is clear when comparison is conducted between the two paradigms of the conditional in Olr. And MW of the PCelt. Verb *kar- "to love" as shown in the following labeled Figure 2.
Source: Tristram (2007)
VI. Developments in Insular Celtic Languages
The Insular Celtic languages are stead to have developed "a rather rigid VSO order just at the time when Vulgar Latin tended towards a fixed SVO word order. It is conceivable that the VSO order in Medieval IC is just a compromise between the conflicting tendencies in the development of fixed word order in VL and Early IC." (Tristram, 2007, p.103) Tristram states that the second position of enclitics in sentences is presumed to have been inherited from PIE via Proto-Celtic then the IC sentences containing enclitics (E) could have one of the structures as follows:
V-E (S O)
V-E (O S)
Furthermore, free word order in sentences without any enclitics was still possible and it is possible that verb-initial structures "could have been generalized at this stage, presumably by extension of the V-E SO patterns and the previously existing structures in which the object preceded the subject (P-E SOV) could have been eliminated because they are impossible in VL, which tended to become a rather rigid SVO language at the same time." (Tristram, 2007, p.104)
Fortson (2005) writes that the look of Insular Celtic insofar as its similarity to the old Indo-European was "dramatically altered by a series of changes to the vowels, in particular the loss of most final syllables, the loss of internal vowels and umlaut." (p.281) the majority of these changes occurred in the common Insular Celtic period however some changes were "later parallel and independent developments." (Fortson, 2007, p.281) the inherited IE verbal morphology is stated by Fortson to be "preserved intact in Insular Celtic" however this is true more so in Goidelic than in Brittonic. (2007, p.281)
The work of Fortson (2007) states that Proto-Goidelic is the prehistoric ancestor of Irish and that this was spoken in Ireland by the Christian era's beginning and perhaps even earlier. The Ogam (Ogham) contained the earliest preservation of the Irish language contained on stone inscriptions written with "strokes and notches chiseled along and across a central line, usually the edge of a stone." (Fortson, 2007, p.282)
Ireland's conversion to Christianity in the fifth century was accompanied by an introduction to the Roman alphabet and the alphabet was taught to Irish clerics by monks in western Britain. During the fifth and six centuries witnessed were "significant alterations to the cultural landscape of the Emerald Isle" as well as changes that were radical in the Irish language and it was "during this time that the Irish changed from looking roughly like Gualish or Latin to looking like Irish." (Fortson, 2007, p.283)
Summary and Conclusion
The examination of the Insular Celtic and Proto-Celtic linguistics has revealed that there are two subgroups of the Insular Celtic language which are those of Goidelic and Brittonic. The Brittonic Insular Celtic includes Welsh, Breton and Cornish and it is believed that it may even contain the language of the Picts. Goidelic and Brittonic are referred to a 'Q-Celtic' and 'P-Celtic' upon the basis of the respective treatment of the PIE labiovelars. This study has also examined the Proto-Goidelic language which is the Irish language's ancestor from prehistoric times and which was spoken in Ireland prior to the advent of the Christian era.
Baldi, Philip and Page, B. Richard (2003) Europa Vasconica-Europa Semitica Theo Vennemann, Gen. Nierfeld, in: Patrizia Noel Aziz Hanna (Ed.), Trends in Linguistics, Studies and Monographs 138, Mouton de Gruyter, Berlin, 2003, pp. xxii + 977. Linguia 116 (2006) 2183-2220.
Ball, Martin J. And Fife, James (2002) the Celtic Languages. Taylor & Francis, 2002.