I think I have to agree with nutty, to me this song seems to be about the irish and scottish and their heritage. I recently read a book on irish history, and maybe I am too much of a romantic, but his poetic lyrics seem very straightforward to me. According to what I have read, irish culture was almost eradicated, and they had to fit in or die, basically. And when that 'lock' was opened, and they were free once again to have their own culture, they did so with a zest. But untill that point, it was remembered in secret, one might even say in darkness. The well on a hill could very well be symbolic of all the ancient places who's meanings have been lost. And, this is ironic to me, I am a 3rd generation celtic-american, so, litterally the child of their children.
And just to add, my parents also dug their well on the upslope of their hill.