That's very odd. I usually see the term 'geek' associated with Sci-fi/fantasy fans. Either way, it's a label I proudly wear!
"Ringer", in the language of the fen (plural of fan), refers to someone who is deep into the lore around the Professor's epic - not just the story itself, which is by and large one of the greatest literary triumphs of the 20th Century - but the methods he used when writing, the languages he created, and the philosophy that molded the Professor's worldview.