The Dennison family probably arrived in Ireland from Scotland during the Plantation of Ulster. There are Dennisons mentioned as part of the retinue of Ludovic Stuart, the 2nd Duke of Lennox who was granted lands at Portlough in the Barony of Raphoe in 1608. The Plantation was initially not a great success and many of the undertakers, finding it difficult to persuade English and Scottish settlers to risk coming to Ireland, let their lands to the native Irish. The crown was not happy with this since it broke both the spirit and the letter of the Plantation Act so a survey by Pynnar was commissioned to ascertain the facts. This was published in 1618 and, in the case of the Duke of Lennox, he is recorded as being the chief undertaker for 2,000 acreas in the Portlough area and as being represented locally by his agent Sir Aulant Aula, Knight
The Duke of Lennox appears in the Muster Rolls of 1631 (now described as being an undertaker of 4,000 acres) and including many Dennisons (under various spellings) under his command. There are also Dennisons mentioned in the Militias of the Bishop of Raphoe and of Lord Chichester in Innishowen
During the Siege of Derry in 1688-1689, many of the local settlers sought refuge within the walls of the city. It would be natural for Dennisons to be among them. When the siege was lifted, the survivors petitioned King William (in a letter dated 29th, July, 1689) for compensation. Among the 142 names listed is that of Robert Dennison
Other Dennisons mentioned in the area from various sources:
As an aside, Thomas Dutton was also a large Undertaker in the Plantation of Ulster. He would later build Dutton's Castle at Drim and who would give his name to the townland of Drumdutton (or Drimdutton).
The following information was kindly provided by Patti Wallace, of Lakeside, Ontario, Canada
My grandmother was Mary Jane DENISON from Leckpatrick near Strabane in Co. Tyrone. She was born in 1879 to William DENISON and Mary Jane DOUGLAS. William had been born in 1845 at Cloghcor, Leckpatrick to John DENNISON (1830-?) and Anne PORTER.
I have found a number of references to Denisons in the area: 1745 Muster Roll for Strabane Barony shows Wm. DENISON of Leckpatrick had 1 gun not in good condition; in the burial ground at Grange Foyle, Dunnalong Parish is the inscription Here lyeth the body of William Denniston who Died the ?? Day of October 1760 aged 83 years – residence is noted as Tamnaclar Donaghedy; in 1796 in A List of Persons to Whom Premiums for Sowing Flax were paid is Andrew Denniston who had 2 wheels; Griffith’s Valuation in Ardstraw, 1860 shows a John Denison and Matthew Denison, while in Leckpatrick there is Eliza Denison who occupies an impressive 42 acres of the Marquis of Abercorn’s land.