A rather fanciful etymology of Fettercairn is given by the late Rev. Robert Foote, in the Old Statistical Account of Scotland, as follows: “Fetter signifies a pass, and there are two large cairns at the top of the mountain and many small ones lower down, near to which, according to tradition, a great battle was fought, from which it is probable that the district got its name.” The tradition referred to by Mr Foote has not reached our day, and we have no record remaining of any particular battle. It may have been one of Wallace’s encounters with the English before his overthrow of them at Dunnottar, or that of Bruce’s victory of the Comyn at the foot of Glenesk, to be afterwards noted in connection with Newdosk.
On the whole, Mr Foote’s derivation is unscientific, because there can be no manner of doubt that the present name Fettercairn is a corruption of the older name Fether, or Fotherkerne; and here, as in many other instances throughout Scotland that can be cited, the local pronunciation follows the older name.
From ‘The History of Fettercairn: a parish in the county of Kincardine‘ by A C Cameron (1899). He also says “The oldest form of the name as written by Wyntoun, Prior of Lochleven, the rhyming chronicler who gives us the story of Fenella and the murder of Kenneth III., is “Fethyrkern.” This term is descriptive of the hillocks and prominent heights lying between the village and Fenella’s castle of Greencairn.” I.e the usual confusion and carping, but it doesn’t really matter.