Analysis of Behind the Hill

Behind the hill I met a man in green
  Who asked me if my mother had gone out?
I said she had. He asked me had I seen
  His castle where the people sing and shout
From dawn to dark, and told me that he had
  A crock of gold inside a hollow tree,
And I could have it.—I wanted money bad
  To buy a sword with, and I thought that he
Would keep his solemn word; so, off we went.
  He said he had a pound hid in the crock,
And owned the castle too, and paid no rent
  To any one, and that you had to knock
Five hundred times. I asked, 'Who reckoned up?'
  And he said, 'You insulting little pup!'