If you poke around, in the last 20 years, they found a mass grave or two full of Irish railroad workers. They'd die while working, and then they'd just make a pile of bodies. When they got enough, they'd just toss them in a pit, cover it, and put the railroad right on top.

Irish history is pretty fucked up. Ireland was settled by Celtic peoples, so they were seen as an easy "other" by their later Germanic neighbors. In all seriousness, it was kind of fucked up for Germanic tribes to raid and enslave people they had mutually intelligible languages with, so they kind of all shifted to primarily raiding and enslaving Celts.

The Irish language had been properly banned in Ireland by England since like the 1500's, if you want to talk about cultural erasure...