O Dennehy or O Denny - Irish / Ua Duineacha. A Sept / Family branch, who had their territory in Co. Kerry in the south - west and Co. Cork in Desmond / Des Mhumhain / Southern Munster and nearby in Co. Waterford in the south - east of the Munster Province.

O Dennery - Irish -  A Sept / Family branch, who had their territory in Co. Mayo and Co. Roscommon in the Connacht Province.

Dennes -

Dennigan or Denegan. Used as variants for Donegan, which see, in the Connacht Province.

O Dennis - Irish / Ua Donnghusa. A Sept / Family branch, who had their territory in Co. Cork in Desmond / Des Mhumhain / Southern Munster and Co. Dublin in the north - east of Southern Leinster? Also see - Denny.

Dennis. From Mac Donagh, which see. Usually known as Dennison in the Ulster Province.

Dennis / le Danei / the Dane. French origins. They were in Co. Cork in Desmond / Southern Munster and Co. Dublin in the north - east of Southern Leinster?

Dennis. French / Dionysius. They were in Co. Cork in Desmond / Southern Munster and Co. Dublin in the north - east of Southern Leinster?

Denny. English origins. They were in Co. Derry in the north - east of the Ulster Province in the 16th Century AD. Cognate with Dennis. Also used in Co. Kerry in the south - west of Desmond / Southern Munster for Dennehy, which see.

O Denroche - Irish / Ua Duibhinnreachtaigh - innreachtach / lawful. A Sept / Family branch, who had their territory in the Connacht Province. Also known as Dunroche.

Denvir. They were in Co. Down in the south - east of the Ulster Province.

Derenzy / de Renzi. They were in Co. Dublin and Co. Wexford in the east of Southern Leinster in the early 17th Century AD.

O Dermody - Irish / Ua Diarmada. A Sept / Family branch, who had their territory in Co. Cavan in Southern Ulster and nearby in Co. Westmeath in the north - west of Northern Leinster.

O Dermody - Irish / Ua Diarmada. A Sept / Family branch, who had their territory in Co. Kilkenny in the south - west of Southern Leinster.

O Dermody or O Darmody - Irish / Ua Diarmada. A Sept / Family branch, who had their territory in Co. Galway in Southern Connacht.

O Dermody. A Sept / Family branch, who had their territory in Co. Tipperary and Co. Clare in Northern Munster.

O Dermody  or O Dermiat  - Irish / Ua Duibhdhiorma or Ua Duryorma. A Sept / Family branch, who were the Chiefs of Breadach at Moville near Inishowen on the western shore of Loch Foyle in Co. Donegal in the north - west of the Ulster Province. Also see next entry.

O Dermond - Irish / Ua Duibhdhiorma - dubhdhiorma / black troop. A Heremonian Ui Cobhthaigh Dal Cuinn "Northern" Ui Niaill Cenel nEogain Sept / Family branch (Descended from 87.Niall of the Nine Hostages the 126th King of Tara / Ireland (Ui Niaill) through one of his (8) sons in *88.Eogan (Cenel nEogain) the 1st King of Aileach in Northern Ulster, and then directly through one of his (5) sons, *89.Felim / Feidhlimidh (Ui Duibhdhiorma) who was to be the direct ancestor of the O Dermond Sept who had their territory at Inishowen in Co. Derry and Co. Donegal in Northern Ulster where they were the Chiefs of Breadach. Many changed to Mac Dermot, and some also to Darby.

Mac Dermot or Mac Dermott - Irish / Mheic Diarmada - dia / god / armaidi / arms. A Heremonian Ui Cobhthaigh Dal Cuinn Ui Briuin Ai Siol Muiredaig Sept / Family branch, who were the Princes of Co. Roscommon and Co. Sligo in the Connacht Province who had their territory at Moylurg / Mag Luirg and were kinsmen to the O Connor Kings of Connacht. Their direct ancestor was *103.Mael Ruanaid "Mor" / Mulrooney "Mor," (a brother to 103.Conor the 38th King of Connacht who is the direct ancestor of the O Connors in the 10th Century AD and the Kings of Connacht and Ireland) and they also had their territory of Moylurg in the north of Co. Roscommon in the east of Connacht, which he had received from his brother. They had their castle on Mac Dermot’s Island in Loch Key near Boyle, and like so many other Gaelic Milesian Families they only survived until the 17th Century AD under the English ethnic and religious oppression when they were driven out of their territory there and forced to move to Coolavin near Loch Gara in Co. Sligo in the north - west of Connacht. Other of their Septs were Mac Dermot "Roe" / Ruadh - of Red Complexion who were at Kilronan in Co. Galway, and Mac Dermot "Gall" in the east of Co. Roscommon. ("The Mac Dermot" the Prince of Coolavin was at one time Niall Mac Dermot). Ancestors - *103.Mael Ruanaidh "Mor,"  *97. Murray / Muiredach "Mullethan" the 18th King of Connacht (Siol Muiredaig), *95.Reilly / Rogallach the 12th King of Connacht (Ui Briuin Ai), *87.Brion the original 1st King of Connacht (Ui Briuin), *86.Eochy "Mugmedon" the 124th King of Tara / Ireland, *80.Conn of the Hundred Battles the 110th King of Tara / Ireland (Dal Cuinn), *37.Heremon (Heremonians).

Fitz Dermot - Normanized - Irish / Mheic Giolla Mo - Cholog / Mheic Gilla Mocholmac. A Heremonian Ui Laoghaire Cu Corb Ui Dunlainge Ui Dunchada Sept who had their territory in Co. Dublin, and in Co. Kildare in Central Southern Leinster. The Ui Dunchada Sept adopted the surname originally of Mac Gilla Mo - Cholmoc and due to their proximity to Dublin in 1170 AD they sided with the Anglo Normans after the Anglo - Norman Invasion and the battle for Dublin and also took up the Norman name of Fitz Dermot (Descended from a son of Dermot). Ancestors  * 103. Dunchad the 15th King of Leinster (Ui Dunchada),  *102.Murrough / Murchad the 14th King of L:einster, *99.Faelan the 10th King of Leinster, *98.Colman "Mor" the 6c King of Leinster, *95.Ailill the 6th King of Leinster, *94.Dunlaing (Ui Dunlainge), *92.Bressal "Belach" the 1st King of Leinster, *90. Cahir / Cathair "Mor" the 109th King of Tara / Ireland, *86. Cu "Corb," *78.Lewy / Lughaidh (Ui Lughaidh), *60.Leary / Laoghaire (Ui Laoghaire) the 68th King of Tara / Erinn,

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