This line, and indeed the whole passage (lines 653-664), allude to the well-known poem by Goethe about the erlking, hoary enchanter of the elf-haunted alderwood, who falls in love with the delicate little boy of a belated traveler.

We touched on the subject of wages, but we didn't reach a conclusion.

I didn't reckon on him having a gun.

The many mansions in one east London house of God.