Ciannachta of Glenn Geimin, of Clann Cian, the O Conchubhair Ciannachta occupied the area of Glinne Gemin (Glengiven, barony of Keenaght, County Derry) with authority from about the 5th century, and were succeeded by the O'Cathains in the 12th century. For more information on the lineage of the Ciannachta, also see Ciannachta Breagh. An early Ciannachta Glinni Gaimen genealogy: (Rawlinson) Conchobor m. Donnchada m. Galaich m. Diarmata m. Conchobuir m. Duind Chuain m. Condálaich m. Máel Fathardaig m. Conchobuir m. Taidg Temin m. Cind Fáelad m. Suibne m. Faílbe m. Ernáine m. Crachíne m. Cormaic m. Eircc m. Etchon m. Findcháin (is é cétnandgab Glenn Gaimen) m. Féicc m. Imchada m. Condlai m. Taidgg m. Céin m. Ailella Auluimb.
- M563, After Eochaidh and Baedan had been two years in the sovereignty of Ireland, they were slain by Cronan, chief of Cianachta Glinne Gemhin.
- U572, The slaying of two descendants of Muiredach i.e. Baetán son of Muirchertach and Echaid son of Domnall son of Muirchertach Mac Erca, in the third yeare of their reign. Crónán son of Tigernach, king of the Ciannachta of Glenn Geimin, was their slayer.
- U616, Death of Suibne son of Crechéne, king of Ciannachta Glinne Geimin
- CS681, Cenn Faelad son of Suibne, king of the Ciannachta of Glenn Geimin, died.
- CS681, Mael Dúin son of Mael Fithrich was slain by the Ciannachta of Glenn Geimin and by Flann Finn son of Mael Tuile.
- U702, Ailill son of Cenn Faelad, king of Ciannachta, died. (Ulster?)
- M752, Tomaltach, Lord of Cianachta Glinne Geimhin, died.
- M755, Conchobhar grandson of Tadhg Teimhin, Lord of Ciannachta Glinne Geimhin, died.
- U757, Fergus son of Congal, Tomaltach, king of Ciannachta Glinne Gaimin, the anchorite Cuidgal, Aildobur, abbot of Muiccert, died.
- M881, Donnchuan, son of Conghalach, lord of Cianachta Glinne Geimhin, died.
- M925, Goach, son of Dubhroa, lord of Cianachta-Glinne-Geimhin, was slain by Muircheartach, son of Niall.
- U1015, Donnchad ua Goaigh, king of Ciannachta, was killed by the Cenél Eógain.
- M1022, Domhnall, grandson of Murchadh Glunillar, lord of the North, was slain by the Cianachta of Gleann-Geimhin.
- M1023, Lochlainn, son of Maeleachlainn, lord of Inis-Eoghain and Magh-Itha, was slain by his own brother, Niall, and the Cianachta of Gleann-Geimhin.
- LC1094, Conchobhar O'Conchobhair, king of Cianachta, in poenitentia mortuus est.
- M1095, Ua Conchobhair, lord of Cianachta-Glinne-Geimhin, was slain.
- M1096, Conchobhar Ua hAinniarraidh, lord of Cianachta, and Ua Cein, lord of Uí -Mic-Cairthinn, fell by each other in a combat. (Ulster?)
- LC1100, Echri Ua Maelmuire, king of Cianachta, was slain by Ua Conchobhair of Cianachta-Glinne -Geimhin.
- LC1104, Donnchadh Ua Conchobhair, King of Cianachta, was slain by his own people.
- M1121, Gilla-Easbuig Eoghain Ua hAinniarraidh, lord of Cianachta-Glinne-Geimhin, was killed by his brothers.
- U1197, A hosting by John De-Courcy with the Foreigners of Ulidia to Ess-craibhe, so that they built the castle of Cell-Santain [and] the cantred of Ciannachta was desolated by them.
- U1197, Mac Gilla-Eidich of the Ciannachta robbed the great altar of the great church of Daire of Columcille and took the four [five] best goblets that were in Ireland therefrom, including 'the gray son' and 'the son of light' and the goblet of Ua Maeldoraidh and 'the twisted goblet' and the goblet of Ua Dochartaich... And he was hanged (namely, at the Cross of the Executions) in reparation to Colum-cille, whose altar was profaned there.
- U1207, A hosting by Hugo De Lacy into Ciannachta, so that he burned the churches of all Ciannachta and seized cows to a countless number.