English was historically the language of power in Ireland, the language of the colonial administrators. They wouldn't have been much bothered about getting Irish names right. If they heard something that sounded vaguely familiar, that's what they'd stick with. If an Irish name reminded them of Helen, they'd be likely to call its owner Helen, and since she was scrubbing the floor at the time, she either wouldn't dare to complain or she'd stay with it in the hopes of gaining some status.
In my part of Africa, Mpho and Mpholokeng are popular girl names, but unlike anything that speakers of Western languages would know. So either the white settlers, in arrogance or ignorance, or the black women, in helpfulness or ambition, tended to change them to Paulina. I wouldn't be surprised if this is a pretty widespread tactic.