the Dublin Census 1851 is an extract of heads of households for Dublin City area only (roughly the area bounded by the two canals). These are the Diggs entries :
West D .Digges,31 Seville Place
Hy. Diggs, 50 Gardiner St. Lower
Joseph Diggs, 43 Bride St.
Rob. Diggs, 13 Oriel St. Upper
Shane