Additionally, I took this to mean how it applies within the context of the plot, symbolism and or motif.
Example:
Professor Sibyll Trelawney: Sibyl was a priestess in ancient Greek mythology. A sibyl (one "l") is a woman who could look into the future. Often sibyls came in groups of 10 and were found in theGreek, Egyptian and Babylonian cultures. A sibyl also can be any female prophet. The name isfrom the Latin sibylla, seer. Trelawney is an English name meaning "for God."
SPOILER ALERT: Please don't read if you haven't read OotP
Here the name is literal, a seer for god and she of course is responsible for the prophecy that dramaticly effected Harry's life. I would then go and look at the role she played within each of the books and the continuing plot line. As noted elsewhere on this board, we fist became aware of the danger of 13 sitting down to eat. You could then discuss the merit of this, how it played out in Phoenix, tie in the Centaurs, etc. You can get pretty detailed if you give it a good try.
at least that my 2 knuts.
and as a bonus, here is a link to a currency converter to wizard money!:
http://cgi.money.cnn.com/apps/hpcurrconv