Wikipedia
Hiberno‐English (from Latin Hibernia: "Ireland") or Irish English refers to the set of English dialects natively written and spoken in Ireland (including both the Republic of Ireland and Northern Ireland).
English was brought to Ireland as a result of the Norman invasion of Ireland of the late 12th century. Initially, it was mainly spoken in an area known as the Pale around Dublin, with mostly Irish spoken throughout the rest of the country. By the Tudor period, Irish culture and language had regained most of the territory lost to the colonists: even in the Pale, "all the common folk… for the most part are of Irish birth, Irish habit, and of Irish language". However, the English conquest and colonisation of Ireland in the 16th century marked a revival in the use of English. By the mid-19th century, English was the majority language spoken in the country. It has retained this status to the present day, with even those whose first language is Irish being fluent in English as well.
Modern Hiberno-English has some features influenced by the Irish language and it also retains some archaic English elements. Most of these are more used in the spoken language than in formal written language, which is much closer to Standard British English, with a few differences in vocabulary. Hiberno-English uses British English spelling and, mostly, British (rather than American) pronunciation standards. However, the various Irish dialects still have their own unique sound systems. Phonologists today often divide Hiberno-English into four or five major dialects or accents, namely: Ulster English, West and South-West Hiberno-English (including, for example, Cork English), Dublin English (often differentiated by local and non-local varieties), and supraregional Hiberno-English.