Throughout it's history, Ireland has always been seen as one of the more rebellious portions of the United Kingdom. Officially joining the United Kingdom after the Anglo-Irish Compromise of 1801 lead to an autonomous Irish state.
The Irish state saw a huge amount of growth as Dublin became one of the most industrialised cities in Great Britain, being host to a huge ship building industry. This level of autonomy allowed cool heads to prevail during the various nationalist uprisings that occurred throughout the late 19th century.
A devolved Parliament was established after the Easter Rising in 1916, due to food shortages and an aborted attempt at Irish independence by a group of radicals calling themselves the IRA.
Thankfully, after years of autonomy in the UK, the Irish people were ambivalent to the demands of the IRA, a few even took up arms with the Unionist sides to prevent the situation from spiralling out of control.
The IRA was successfully put down after an huge offensive in the Irish countryside which eventually lead to the Good Friday Agreement in 1920, giving the Irish people more autonomy. This was eventually extended to the other Celtic nations in the UK by 1935.
Today, many Irish people consider themselves both Irish and British, much like the Welsh, Scots and Cornish peoples in the rest of the UK.
Irish and English are the two official languages of the United Kingdom. Due to the potato famine never taking place in Ireland, the language has survived into the 21st century as a fully functioning one on par with OTL languages such as English and French. Irish is a Celtic language that is mainly related to Manx and Gaelic, while also being distantly related to Cornish, Welsh and Breton.