Other branches of the clan: Donagh, Donogh, Doneghy, Donoghey, Donaghy, Donat, Denison, McDona, Donough, MacDonough, MacDonogh, McDonnagh.
Irish Clan Name: MacDonnachadhad

The Gaelic personal name Donnchadh or Donagh (Donal or Donald in English) became incorporated into the family name MacDonnachadha, which means "son of Donagh". Although Donagh was a popular personal name throughout the island of Ireland, the family name derived from it was not as evenly spread.

One MacDonagh family were a Sept of the powerful MacCarthy Clan and Lords of Duhallow. These MacDonagh chieftains held a "strong castle" at Kanturk in County Cork, in the southern Irish Province of Munster. The name MacDonagh is now rare in that region and it is believed that some of those families in later times took the name of their ruling clan.

Notable bearers of the family name were John MacDonogh (1779-1850), born in America of Irish parents, who was a philanthropist who campaigned tirelessly for the abolition of slavery; Irish-America Thomas MacDonough (1783-1825) who became famed for his bravery at the Battle of Plattsburgh during the American War of Independence; and Thomas MacDonagh (1878-1916). This last Thomas was a poet and a signatory of the Irish Declaration of Independence, he was later executed by the British for his part in the Easter Uprising of 1916.

Highwood is part of the ancestral home of the MacDonaghs in Ireland and forms a stage of the Beara-Breifne Greenway which is based on the historic march of O'Sullivan Beara in 1603.