Letterkenny is the largest and most populous town in County Donegal, Ireland. Its English name is derived from the Irish name Leitir Ceanainn,
meaning "Hillside of the O'Cannons" – the O'Cannons being the last of
the ancient chieftains of Tír Conaill. With a population of 19,588, Letterkenny is located on the River Swilly in east Donegal. Letterkenny, along with the nearby city of Derry, forms the major economic core of the north-west of the island of Ireland.