Graham, the song is called the Massacre of Glencoe. It commemorates a situation whereby the clan MacDonald gave guest priviledges to its' enemy the Campbells. Inviting them to stay over night in their own castles, the MacDonalds did not realize the Campbells were in the employ of the English who wanted their lands.

According to legend, most of the MacDonalds were slaughtered in their sleep when the Campbells arose and took the castle. Ostensibly they were carrying out orders of the English King who had outlawed the MacDonalds.

It's never been forgotten. The song itself was written some time after, but as you can see, the feelings are still quite strong.