Beatty is a surname of Scottish and Irish origin. In some cases from Bartholomew, which was often shortened to Bate or Baty. Male descendants were then often called Beatty, or similar derivations like Beattie or Beatey. The name Beatty or Beattie, others think, arose in Ireland from Betagh, a surname meaning hospitaller. A majority of people named Beatty or Beattie in Ireland are the descendants of Scots who came over to Ulster in the seventeenth century. Beattie is common in counties Antrim and Down, whilst Beatty is more common in counties Armagh and Tyrone. In Fermanagh in 1962, Beatty was the fifteenth most common name and was recorded as synonymous with the names Betty and MacCaffrey (or McCaffrey).
It is most likely that the name derives from Mac a'Bhiadhtaigh, from biadhtach, "one who held land on condition of supplying food (biad) to those billeted on him by the chief". In the rest of Ireland, the name Biadhtach (Betagh; "public victualler") was changed to Beatty or Beattie. In Scotland, the Beatties were a reiver clan in the Langholm area of Eskdale. George MacDonald Fraser has written about the reiving clans in "The Steel Bonnets : The Story of the Anglo-Scottish Border Reivers".
An Irish origin of the name Beattie is supported specifically by the Irish-specific marker S169 which is most common in Leinster, Ireland, but also "found in Scotland, especially among men with the surnames of Beattie and Ferguson".