O Delargy - Irish - Ui Duibhlearga - learg - plain or slope. A Sept - Family branch who had their original territory in Co. Mayo in mid - western Connacht and later migrated to Co. Antrim in north - east Ulster before the mid - 17th Century AD.

Delea or Delay - See Dunlea.

O Deloughery - Irish - Ui Dubhluachra - dubh - black. A Sept - Family branch who had their territory in Co. Cork in Southern Munster. 9 different Spellings used there including Deloorey & Dilloughery and a synonym - Dilworth.

O Dempsey - Irish - Ui Diomasaigh - diomasach - proud man. A Heremonian Cu Corb Clann Maellugra Clanmalier Sept - Family branch who had their territory in Co. Laois & Co. Offaly in mid - western Leinster. They are originally descended from *60.Laoghaire "Lorc" who in 593 BC was the Heremonian 68th King of Tara - Ireland who was a son of the *59.Ugaine "Mor" - the Great the previous 66th King of Tara - Ireland. In 120 - 123 AD his descendant, *88.Cahir - Cathair "Mor" was the 109th Heremonian Cu Corb King of Tara - Ireland who was killed at the Battle of Moigh Acha and his son 89.Fiacha "Ba hAiccid" was made lame. Another son, *89.Ros "Failge" is the ancestor of the Ui Failge - Ui Conchobair Failghe - O Connor "Faly," Ui Riacain - O Dunnes, and the O Dempseys from the Clann Maellugra. Another son, 89.Criffin - Crimthann is the ancestor of the Ui Crimthainn Ain - O Duffs. Another son, 89.Daire "Barrach" is the ancestor of the Ui Bairrche - Mac Gormans. Another son 89.Ailill "Cetach" is the ancestor of the Ui Cheithig - Crich na Cetach Sept. Another son, 89.Bressal "Enechglas" is the ancestor of the Ui Enechglais - O Fearys. The O Dempseys were Kings & Chiefs in their territory at Clanmalier between Co. Laois & Co. Offaly in mid - western Leinster where they were strong Irish Patriots. In the 12th Century AD O Dempsey actually defeated Strongbow in battle during the Anglo - Norman Invasion. Because of their geographic situation to The English Pale they also were to eventually succumb becoming acting English Viscounts & Barons. During the Elizabethan Wars they were to side with Elizabeth 1st and later James 1st to hold onto their territory there and because of this Terence Dempsey was appointed the English Viscount Clanmalier. In 1689 AD their Irish Chiefs were situated at Geashill in Co. Offaly on both sides of the River Barrow and seeing a light at the end of the tunnel for Ireland they sided with the Catholic English King James 11 and lost their territory there to the English anyway who gave it over to Lord Digby who renamed their castle after himself. They were also in Co. Kildare in Central Leinster and  always came under intense pressure from the English who were always trying to expand The English Pale around Dublin. Maximilian O Dempsey, who was also known as the English Lord Viscount Clanmalier, who died on 30. 11. 1690 AD, was to be the last of their Irish male line who were to be the  Gaelic Milesian Princes of Offaly. Ancestor *84.Cu "Corb."

Dempster - Manx origins - judge. They were in Co. Down in south - east Ulster. Also used as a synonym for Dempsey, which see.

Denieffe - English origins. They were in Co. Kilkenny in south - west Leinster since the 18th Century AD. Sometimes shortened to Neef.

Denivan - See Dingevan.

Denn - They were in Co. Waterford in south - east Munster & Co. Kilkenny in south - west Leinster. Also see de Denne under Deane.

O Dennan or Dennany or Denneny - Irish - Ui Doineannaigh - doineannach - tempestuous. A Sept - Family branch who had their territory in Co. Cavan in Southern Ulster and the surrounding Counties.

                                                                                 +On to  Dennehy - Dermot