Looking for Irish Jewish ancestors? Here's an interesting article that may provide some answers.
The first article in Familia: Ulster Genealogical Review is 15 pages, with footnotes, and titled "Researching Belfast Jewish Families, c. 1850-c. 1930" by Pamela McIlveen and William Roulston.
Some mentioned surnames are JAFFE, HERZOG, ATTIAS, BENSELUM, BENGGIO, PARIENTE; family origins include Prague, Mecklenburg and Gibraltar.
The Belfast community's founder - in 1809 - was Daniel Joseph Jaffe, born in Mecklenburg.
The article offers resource suggestions to help find more information.
Thanks to Ann Rabinowitz for this clue - it is a fascinating read, even if you aren't searching Belfast or the Jaffe family.