O Diamond or O Dimon or O Dimond - Irish – Ua Diamain. An Erenagh Sept - Family branch - who had their territory in the east of Co. Derry in the north - east of the Ulster Province and are now also in Co. Donegal in the north west of Ulster and nearby in Northern Connacht.

Dick - Richard - Scottish origins. They came into Ireland in the 17th Century AD into Co. Antrim & Co. Down in the east of the Ulster Province. Dix was also used a synonym.

O Diffin - Used as a variant for Duffin, which see, in Co. Armagh & Co. Tyrone in the Ulster Province.

O Diffley or O Duffley - Used as variants for Devilly, which see.

Mac Digany or Mac Digney - Irish – Mheic an Deaganaigh. See Deane.

Digby - English origins. In 1689 AD they were granted the territory and Castle of the Irish O Dempsey Chiefs, by the English.

O Diggin - Irish - Ua Duibhginn - dubh - black / ceann - head. A Sept - Family branch - who had their territory in Co. Kerry in the south - west of the Munster Province. Usually pronounced Duigan & Deegan elsewhere.

O Dilgan - Irish - Ua Duibhleachain. A Sept - Family branch - who had their territory in Co. Clare in the north - west of the Munster Province. Cognate with Dullahan.

Dill - English origins. They were in Co. Donegal in the north - west of the Ulster Province in the early 17th Century AD.

O Dillane - Irish - Ua Duilleain. A Sept - Family branch - who had their territory in Co. Limerick in the mid - north - west of the Munster Province and in the north of Co. Kerry in the south - west of Munster. Some changed to Dillon, which see. Also used as a variant for Delane, which see.

O Dilleen - Irish - Ua Duillin. Used as a variant for Dillane, which see, in Co. Clare in the north - west of the Munster Province and nearby in the south of Co. Galway in Southern Connacht.

Dillon - English Barons. They were in Co. Westmeath in the south - west of Northern Leinster & Co. Galway in Southern Connacht at Loch Glinn where there is their original Family residence, which is now used as a Franciscan Convent for the Missionaries of Mary.

Dillon - Diolun - Norman Breton origins - (Descended from Sir Henry de Leon) who arrived into Ireland in 1185 AD. They took over control of Co. Longford & Co. Westmeath in the west of Northern Leinster where it was later known as Dillon’s Country. 3 separate branches of English Earls who were in Co. Roscommon & Co. Mayo in the Connacht Province & Co. Meath in the south - east of Northern Leinster & Co. Longford in the north - west of Northern Leinster. Also see Dillane.

O Dinan or O Dynan - Irish - Ua Daghnain. A Sept - Family branch - who had their territory in Co. Tipperary in the north - east of the Munster Province. They were the Chiefs of Uaithne whose territory was in the Barony of Owney Beg in Co. Limerick in the mid - north - west of Munster. They are now in Co. Clare & Co. Cork in Munster. Some of the Dynans in Co. Cork also changed to Dinneen.

O Dinane - A Sept - Family branch - who had their territory in Co. Cork in Southern Munster.

                                                                                    +On to Dinerty - Dixon