It is essentially "The Ferry"
. Basically, The Potato Famine happened and a lot of Irish people effectively became refugees, and Liverpool was the main port. Plenty moved on of course but obviously a certain percentage "stuck" (as Liverpool was an industrial city and employed them as labourers).
'member in the best movie ever Titanic, the Irish guy Tommy insists that "Irishmen built this ship" even though it was built in Liverpool. That's because by the time Titanic was being built, pretty much the entirety of the manual labour in the Liverpool ship building industry was Irish.