From: Early Irish History and Antiquities and the History of West Cork By Rev. W. O’Halloran 1916, O’Donovan Genealogy.

The O’Donovans of Cork
This old family was expelled from their ancient seat Cairbre Aebha near Killmalock, towards the close of the 12th century, by the Fitzgeralds, and settled in the district around Drimoleague, after defeating the old settlers. The clan title Carbre was transferred to the new territory, and, in course of time, it extended to the whole district now known as the barony of Carbery. The territory included two manors, Castledonovan and Rahine.
Crom O’Donovan was the ancestor of this family. He built a castle on the banks of the river Maigue, near Killmalock, and was killed, 1254, near Iniskeen in a conflict with the O’Mahonys.
Cahil, the son of Crom, drove out the O’Driscolls, and the territory he conquered, which comprised 67 ploughlands, was called Clancahill. He was succeeded by his son Donnell, who built Castledonovan in 1560. In 1650 the castle was attacked by Cromwell’s soldiers and the garrison—their munition being exhausted—escaped in the night time, and fled to Limerick. The walls are still standing, but it seems it has not been inhabited since the attack.
The castle of Rahine was built by Donnell II., who succeeded his father in 1584. This castle was also battered and destroyed by cannon balls by the Cromwellians. The territory was forfeited in consequence of their adhesion to the royalist cause. At the Restoration Donnell IV. petitioned Charles II. to restore him to his estates. The king referred the matter to the Irish Government, with the result that a portion of the manor of Rahine was restored to him, while the manor of Castledonovan was granted to Lieutenant Nathaniel Evanson. In the early part of the reign of James I. a grant was made to Donell O’Donovan of Castledonovan, gent., and a large tract of country therein specified, together with all customs, royalties, dues, and privileges, due and payable to the said Donell and his ancestors, in the ports, bays, or creeks of Castlehaven, Squince, Conekeogh, and the western part of Glandore; saving to Donell McCarthy (Reagh), the king’s ward, all chief rents, customs, and privileges due or payable to any of his ancestors. Part of those lands were created the manor of Castledonovan, with five hundred acres in demesne to hold of the Castle of Dublin, in common soccage.
Donal V. O’Donovan made a provision in his will that in case his children died without issue the reversion of his estates was to go to Morgan O’Donovan, grandfather of the O’Donovan Lissard. Richard, eldest son of Donal married in 1800 Emma Anne Powel, a Welsh lady, and had no children. He died in 1829 and with him the senior branch of the O’Donovan family became extinct. He got his father’s will upset and willed his property to his wife, who willed it to her brother, Major Powel.
Smith in his History of Cork relates the following story:—” Clancarthy, McCarthy Reagh, and O’Donovan, having joined their forces, went into the County of Limerick to plunder, as was the custom of former times. They brought a considerable prey to the Castle of Blarney, the seat of Clancarthy, who was for having all the cattle drove into his own bawn, without sharing the spoil, and in this manner he had served McCarthy Reagh before, who then lived in the Castle of Killbratain, and who on this occasion called upon O’Donovan to join him, that he might assist him if Clancarthy did not share the booty. O’Donovan immediately opposed the driving in of the cattle without dividing them, whereupon a contest ensued, Clancarthy, being thrown down by O’Donovan, had his weapon drawn, intending to kill his antagonist; but O’Donovan perceiving his design, wrenched it from him, and with it slew Clancarthy on the spot, and divided the spoil with McCarthy Reagh. It is not certainly known when this event happened, but the instrument, with this tradition relating to it, is time out of mind in the family. It was a class of weapon of ancient Irish origin, called the cladagh, and was somewhat similar to the Highland dirk. This weapon is supposed to come originally from the Spanish Miguelots, from whom, according to antiquarians, the Milesian Irish derived them, and afterwards handed them over to the Scots.”