McCoy and Galloglass are both Anglicisations of terms from what language?
Gallowglass The gallowglasses (also spelt galloglass, gallowglas or galloglas; from Irish: "gall óglaigh" meaning foreign warriors) were a class of elite mercenary warriors who were principally members of the Norse-Gaelic clans of Scotland between the mid 13th century and late 16th century. As Scots, they were Gaels and shared a common background and language with the Irish, but as they had intermarried with the 10th century Norse settlers of western Scotland, the Irish called them "Gall Gaeil" ("foreign Gaels").
Flaith A flaith (Irish) or flath (Modern Scottish Gaelic), plural flatha, in the Gaelic world, could refer to any member in general of a powerful family enjoying a high degree of sovereignty, and so is also sometimes translated as lord or aristocrat in the general sense, or can refer to sovereignty itself. Thus it did not usually refer to a specific position such as "Rí" (king) which any given "flaith" might or might not hold, allowing for the term to eventually develop the slightly alternative meaning of any hereditary high aristocrat who was understood to be subordinate to the king. In this later sense a "flaith" was similar to a magnate or Grandee.