Earnside, an ancient forest in Dunbarny parish, SE Perthshire, and eastward thence, along the Earn and the Tay to the eastern border of Abdie parish, around Lindores Abbey, in Fife. It is said by Sibbald to have been 4 miles long and 3 broad, but it could not have been less than 8 miles long, and, though taking name from the river Earn, it extended so far beyond that river's present confluence with the Tay as to countenance a tradition that the Earn once flowed to the base of the hills in the NW of Fife, that the Tay closely skirted the heights which now screen the N side of the Carse of Gowrie, and that the two rivers did not unite till they reached a point considerably to the E of their present confluence. Earnside Forest was the traditionary scene of adventures of Sir William Wallace, notably of a sanguinary conflict which he maintained within it against the English; and it was sometimes called `Black Earnside,' a name referring probably to the dense gloom of its trees. It was long ago destroyed, but large masses of black oak, supposed to be remains of it, are found imbedded in the soil of various parts of the territory which it once occupied.

(F.H. Groome, Ordnance Gazetteer of Scotland (1882-4); © 2004 Gazetteer for Scotland)