Caber Feidh is one of the earliest known Scottish Reels; it's first documented appearance was in a collection known as the "Drummond Castle Manuscript" (A Collection of Countrey Dances written for His Grace the Duke of Perth by Dav. Young, 1734). It was later published in a host of tunebooks, notably the Gow Collection (vol. 4, c. 1800) and the Skye Collection (1887). It may well have been the latter work that introduced the spelling now most common.
Almost all the versions of Caber Feidh that were collected on PEI came from Kings County, where the tune had probably been in circulation since the early days of Scottish settlement. A 1950s-era recording by Cape Breton fiddler Winston "Scotty" Fitzgerald also contributed to the continued local circulation of the tune.
Of special interest: a three-part variant of the tune is sometimes played in Central Kings County (see versions by Allan MacDonald, Francis MacDonald, and Hector MacDonald). The third turn is essentially an octave-lower variation of the high-turn.
Notation for Allan MacDonald's version of this tune is available here.