MacDonnell, Macdonnell, or McDonnell is a surname of Scottish and Irish origin.It is an anglicized form of the Gaelic name Mac Domhnaill, which means son of Donald (Scottish) or Domhnall (Irish). Alestair Ruadh MacDonnell (1725–1761), Scottish chief of Glengarry, secret agent and spy on Prince Charles Edward after 1750. 2  Alexander McDonnell, 9th Earl of Antrim (born 1935), British peer from Northern Ireland. 3  Alexander McDonnell (1798–1835), Irish chess master.