Many ethnic groups found their way into Ireland, some eventually became know as "more Irish than the Irish themselves." Some of these include:
WELSH - The name "Walsh," (in Irish, Brannagh or Breathnach), meaning a Briton or Welshman, is found early in Cork, Dublin, Kerry, Kilkenny, Tipperary, Wexford, Waterford and Galway. The name remained numerous in Cork, Mayo, Waterford, Galway, Dublin and Wexford in 1890. Some Welsh families in Ireland: Howell, Lawless, Lillis, Lynagh, Lynott, Merrick, Hore, Cod, Stafford, Whitty, Rossiter, Sinnott, Stephen, Quiney, Walsh.
GERMAN PALATINATE - Families came to Ireland in the 18th century from the Palatinate of the Rhine in Germany. In 1709 some 7,000 of these refugees arrived in England. Thousands were sent to North America, settling in Pennsylvania and North Carolina. In Ireland, they are found centered in Co. Limerick, but many moved on to America after settling in Ireland. Names include Baker, Bovanizer, Bowen, Doube, Delmege, Gilliard, Smyth, Latchford, Ligier, Millar, Lodwig, Modlar, Pyper, Heavenor, Reynard, Ruttle, Shire, Stark, Switzer, Teskey, Neazor.
CORNISH - Cornish, or Briton families are found in Ireland under names like Jagoe, Lanyon, Pascoe, Pender, Pendred, Penrose, Vivian, Tredennick, Tresilian and Trevelyan.
HUGUENOT - French and Fleming Huguenot families settled in the latter 17th centry at Dublin, Kilkenny, Waterford, Cork, Portarlington and Lisburn. Noted for making linen, cloth and lace, etc. Some families included Barre, Blacquiere, Boileau, Chaigneau, Du Bedat, Champion, Chenevix, Corcellis, Trench, Crommelin, Delacherois, Drelincourt, Dubourdieu, Du Cros, Fleury, Gaussen, Logier, Saurin, Guerin, Hazard, Hassard, La Touch, Le Fevre, Lefroy, Lefanu, Maturin, Perrin.
DANISH (Viking) - The Danes (Lochlainders, Ostmen, Vikings) had colonies in Ireland for over centuries. Centered in Dublin and Meath ( in Fingall) and in Wexford, Waterford, Cork and Limerick, they settled on the coasts of Ireland from the 8th century. Some old settler names include Betagh, Coppinger, Dowdal, Drumgoole, Gould, Harold, Palmer, Plunket, Skiddy, Sweetman, Trant, Ost.
JEWISH - Found resident in Dublin and other larger cities earlier, many Russian and Polish Jews settled on the south side of Dublin city from 1881-1890. Family names included Coplan, Fridberg, Greenberg, Hesselberg, Maisell, Matufsky, Rabinovitch, Rossin, Statzumsky, Stuppel, Wachman, Wedeclefsk, Weiner, Winstock.
More information on ethnic surnames can be found in "The Book of Irish Families, Great & Small," IGF.