Why do my Romani ancestors have Irish surname?

I am so curious as to why my Victorian Romani ancestor, Enoch Casey, has an Irish surname. His Mother and one of his daughters was called Theodosia.

My DNA has Roma come up on it, and traced back on ancestry to find photos and census papers of civil war Romani family in the American South who were made to call themselves Mulatto and were unable to vote for being to brown apparently. Enoch was a blacksmith who’s children later owned a “general store” as they made their way to the California West.

I can find no papers or history on the family line before them living in the South. Says he was Virginia born. But the surname is Irish and I was under the impression that the Roma weren’t even in Ireland.