is not a sept, or clan, name, but rather an individual patronymic passed down through various, yet discrete, colonial families arriving at different times in Irish history.

Some families "went native" during the Gaelic revival of the 14th and 15th centuries, and many refused to endorse the Protestant Reformation.

Of the Pale Fitzsimons, it is thought discrete branches settled at Tullynally, County Meath, the line of Sir William Johnson and 'went' native by intermarrying with the O'Reillys and MacMahons of south central Ulster.

The English family which sent its youngest son to Dublin in 1323 died out in the name, only the Irish branch now survives.

These originating in Norfolk, Lincolnshire and Nottinghamshire are thought to be Scandinavian and of the genere Danus, as the area was settled by Danish Vikings and predate the Norman invasion in 1066 AD.