I live in Portlaoise (formerly Maryborough) and while I cannot provide a Genealogy service, I can advise people on aspects of our town's history. If your ancestors came from or near the town, have a look at www.portlaoisepictures.com to see hundreds of images of how the town looked years ago and what it's like today.
“The principal castle of the Dunnes was built in Tinnahinch in the old parish of Rearymore (east of Clonaslee) by Tadhg MacLaighnigh Ui Duinn who ruled the territory in 1475. It was the residence of the chief of the Dunnes. A map made in 1563 shows this castle (Baun Riaganach) to be near the source of the river Barrow. The castle was located about one mile south of Tinnahinch Bridge beside the river Barrow. The place name Tinnahinch comes from "Tigh-na-hlnnse" or "house of the island." A fairly large stream flowing into the Barrow at the site of the castle almost surrounds it, creating the impression of an island. It is believed that the castle was on the west side of the river and, of course, this is in line with the place name description above.
In fact, the field on the opposite (east) side of the Barrow was known locally as the Mill Field. In 1547 the forces of Anthony St. Leger, the Lord Chief Justice, built a fortification around Baun-Riaganach in order to oppose the O'Connors and O'Moores. The castle was attacked and blown up by Cromwellian forces under Colonel Hewson in 1653. It was occupied by Charles Dunne, possibly the Catholic son of Barnaby Óg, who took part in the Confederate Wars (1641 - 1649). Very strong resistance from Charles resulted in Colonel Hewson using a full park of artillery to level the castle. Dr. O'Donovan, in his Ordnance Survey Letters for the Queen's County (1838), stated that "The present ruins of this castle are very trifling, but it was certainly, when perfect, a castle of considerable importance and extent." There is very little trace of it today with the possible exception of an old wall which may have formed part of the structure.”1
“Riaganach is identified in a location name, mbád.ún riaganac., as "Badhun-Riaganach, i.e. the bawn of the Hy-Regan which was the tribe-name of the O'Dunnes, in the barony of Tinahinch and Queen's County" in 1547.”2
“Badún : n o, m. (ba (pl. of bó) + dún ?) enclosing wall, fortified enclosure (for protection of cattle.”3
...[It] was not until 1563 that a comprehensive settlement of [Laois and Offaly] took place. This revamped colony differed slightly from its failed predecessor in that it included grants of land to select and amiable Gaelic tenants [indigenous people]. Aside from the obvious strategic purpose, the colony was now to serve a reforming or exemplary function whereby the native population were to be introduced to the benefits of English 'civility.' The hope was to draw Gaelic Irish to 'civility' by allowing them to participate in a 'model' English colony. To guarantee this societal transformation, all the settlers, including the Gaelic Irish, were to adhere to a strict set of conditions which required them to use English language, dress and customs, and not to make use of the Gaelic brehon law system or to maintain Gaelic military men…
...the majority of the English grantees were in fact the very soldiers who had been serving in the area, and who had already acquired a reputation for brutality and greed amongst the native population. This brutality and greed was officially sanctioned, as Lord Deputy Sussex increasingly resorted to the use of martial law. This form of régime was cost-effective because the commissioners were licensed to collect the profits of their work. Commissions of martial law 'legally' entitled the bearer to a third of the moveable goods and possessions of the dead 'traitors.' According to David Edwards1, "this acted as an incentive to slaughter: the more 'suspected traitors' the commissioners killed, the more traitors' goods they and their followers received...2
1 David Edwards,'Beyond reform:martial law and the Tudor reconquest of Ireland'in HistoryIreland,v,no.2 (1997),pp16-22.
2 John Derricke's "Image of Irelande", Sir Henry Sidney, and the Massacre at Mullaghmast, 1578
The Image of Irelande by John Derricke Review by: Vincent P. Carey, Irish Historical Studies, Vol. 31, No. 123 (May, 1999), pp. 305-327. From JSTOR.
2 http://medievalscotland.org/kmo/AnnalsIndex/DescriptiveBynames/Riaganach.shtml. John O'Donovan, Annals of Ireland, by the Four Masters, Volumes 1-7 (New York, N.Y.: AMS Press, 1966), vol. 5, p. 1502, footnote "m"