The words are by Andy Stewart, about 1960 as I remember (he introduced it on the Scottish TV programme "The White Heather Club", I think. He took his hint from the title of the pipe tune, which was composed [or I should say adapted for the pipes] by John Macleod, 93rd Highlanders, during the Crimean War, after listening to a Sardinian band playing a continental tune. The theme, from an Alpine folk tune, had been used also by Rossini in the William Tell ballet music. Macleod's version is in a good few books of pipe tunes, e.g. Scots Guards Standard Settings, 218 [with the harmony ("seconds") as well]. BTW there's another set of words that was sung by the Inverscotia Singers, in Patriot Songs for Camp & Celidh, "The Green Hills", beginning "Oh the green hills are calling me" chorus, "For the calling of the hills I hear" etc.