A
Celtic folk song about a
poor guy whose
girlfriend dies, probably of
whooping cough or
something, and he
camps out every
night on her
grave.
Recent versions have been performed by Dead Can Dance and Sinead O'Connor. Dead Can Dance dropped the verses about how this girl died a virgin despite this one scandalous evening the couple almost had in a blackthorn shrub.
In all seriousness, it is one of the saddest, most beautiful songs I've ever heard (depending on the performer, I'm a bit partial to Dead Can Dance); it's right up there with In a lonely place by Joy Division/New Order.