Who is the old man, and what is his name? What Biblical references does this imply, and why would the author include these in the story?

The old man at the beginning of the book who sets the boy on his journey identifies himself only as "the king of Salem". Salem is an ancient name for Jerusalem. In the Book of Genesis from the Bible, the king of Salem is named Melchizedek and he is also identified as a priest from whom Abraham accepts a blessing and gives a tithe of 1/10 of all his possessions.