Yes, it's down to whether you're a Gullion or a Gallion. I go for Sliebe Gallion, in the Sperrin Mountains in the region they call Derryveagh. The hill itself is the most southerly and easterly in the range, so I guess that puts it in Tyrone.

Unfortunately the link changes frequently so you have to use the search to find the actual hill.

The name apparently means "Mountain of the Heights" so it's a bit disappointing to find it is 150 meters lower than the highest in the range, and only the 397th highest in Ireland! It sounds much higher in the song.