Wikipedia
Donnchadh
Donnchadh is a Gaelic masculine given name. It is composed of the elements donn, meaning "brown"; and chadh, meaning "chief" or "noble". The name is also written as Donnchad, Donncha, Donnacha, Donnchadha and Dúnchad. In English it is pronounced "Dun-uhh-kah" or "Done + Acka".
Modern versions include (in Ireland) Donagh, Donough, Donogh and (in Scotland) Duncan. Also anglicised as Dennis or Denis and Dionysius.
The surnames Donough, McDonagh, McDonough, O'Donoghue and Dunphy among others are derived from the given name (In Gaelic: Mac - son of, Ó - of the family of). Another derivation is the name of the Scottish Clan Donnachaidh.