Irish was the majority mother tongue in Ireland up until the 1800s. There's a few reasons why English was becoming more widely spoken, in brief:

• British education: The 'National Schools' instituted in the early 19th century by the British government, who ordered that English only was to be taught right up until 1871.

• Church and political advice: The Catholic Church had a monopoly over many aspects of life in Ireland and urged people not to use Irish, and this was done quite effectively through the schools which they run. The Church did not begin to promote worship in Irish until 1914. Political leaders also thought that the Irish language was a backwards part of culture.

• The Famine of 1842: The potato blight struck worst rural areas in the west of Ireland, where the Irish language was proportionately most spoken. The eastern and middle parts of Ireland were not affected so badly by the famine, and they had been speaking in the English language since the 16th century in any case. When people were fleeing Ireland during the famine, they weren't speaking Irish.

• Economic Advantage: This is one of my favourite arguments from one of Linda Colley's works - a lot of the time in the early United Kingdom, people chose to speak English over the language or dialect which was common in their area for the economic prosperity it might have brung. Thus, with the emigration from Ireland in the 1840s to Great Britain and the United States most commonly, it was sensible to speak English and have your child get into the habit of conversing in it. The perception of Irish as backwards and ancient did not help sustain it.