Dunne or Dunn is an Irish surname, derived from the Irish Ó Duinn and Ó Doinn, meaning "dark" or "brown." The name Dunne in Ireland is derived from the Ó Duinn and the Ó Doinn Gaelic septs who were based in County Laois, County Meath and County Wicklow. These septs in turn are descendants of the O'Regan noble family. It is in these counties that the majority of descendants can still be found. Hundreds of years ago, the Gaelic name used by the Dunn family in Ireland was Ó Duinn or Ó Doinn. Both Gaelic names are derived from the Gaelic word donn, which means "brown".
https://en.wikipedia.org/wiki/Dunne