Magennis

Magennis, also spelled Maguiness, Maginnis, McGuinness or Guinness, is an Irish surname, derived from the Gaelic Mac Aonghusa, meaning the "descendants of Angus", which in eastern Ulster was commonly pronounced as Mag Aonghusa. A prominent branch of the Uíbh Eachach Cobha, the Magennises would become chiefs of the territory of Iveagh, which by the 16th century comprised over half of modern County Down, Northern Ireland. By the end of the 17th century, their territory had been divided up between them and British prospectors.