Carthach was a contemporary and bitter rival of High King Brian Boru, and what would become known as the McCarthy Clan was pushed out of its traditional homelands in the Golden Vale of Tipperary by the expansion of the O'Brien sept in the middle of the twelfth century.

Each of these families continued resistance to Norman and English encroachment up to the seventeenth century when, like virtually all the Gaelic aristocracy, they lost almost everything.

An exception was Macroom Castle, which passed to the White family of Bantry House, descendants of Cormac Láidir Mac Cárthaigh.

Another male forename similarly associated with them is Finghin, anglice Fineen, but for some centuries past, the name Florence (colloquially Flurry) has been used as its English form.

Until the dissolution of the kingdom in 1596, the crown was vested in the hereditary possession of the Mac Carthy Mór (by the law of tanistry).

The MacCarthy Reagh seated themselves as kings of Carbery in what is now southwestern County Cork including Rosscarbery in the 13th century.