Lyric discussion by elenoftheroads 

Cover art for Tam Lin lyrics by Fairport Convention

Although Sandy Denny actually sings "Carter Hall", it refers to Carterhaugh forest, an area of land it is presumed by many commentators to be owned by the heroine of the song. This is why she tells Tam Lin that she'll come and go as she likes - he's basically squatting on her property.

<a href="http://en.wikipedia.org/wiki/Tam_Lin">Wikipedia</a> has more info and sources.

Link(s)

OK, so I b***ered up the code. http://en.wikipedia.org/wiki/Tam_Lin