Found on the bagpipers’ forum: From Principles of English Etymology (1887) by Walter W. Skeat, a professor of Anglo-Saxon at Cambridge: In the chapter on "Words of Gaelic Origin," he has a section (408) on three "special" words, one of which is "pibroch." Here's what he says:
As to pibroch, it is merely English in a Gaelic disguise. The Gael. Words piob, piobair, are merely the English words pipe, piper, borrowed from English in the sixteenth century. 'From the later, by the addition of a Celtic termination was formed the abstract noun, piobaireachd=piper-age, piper-ship, piping.... When the Sasunnach, having forgotten his own pipership, reimported the art from the Gael, he brought with it the Gaelicised name piobaireachd, softened into pibroch, where the old English piper is so disguised in the Highland dress as to pass muster for a genuine Highlander.'
The secondary quote is sourced: The Dialect of the Southern Counties of Scotland (1873), J.A.H. Murray, p. 54.
No, it is more like a style of playing than a special instrument. I find it quite irritating, actually, even for Great Highland bagpipes--which is saying something. In other words I think it's mostly the same instrument as it used to be. Well... they probably don't use actual animal bladders in modern bagpipes.
Pronounced "PEE-brok." Believe it or not. This is a Scots Gaelic term that distinguishes traditional bagpipe music from the type more commonly played today.
Wikipedia sez: "In Scottish Gaelic, the original form for the name of this type of music is pìobaireachd (literally meaning "pipering" or "pipery", or the actions of a piper), and the Anglicized word pibroch is derived from the Gaelic pronunciation: (ˈpʰi�?bərɒχk)."