It's possible that:
* You've encountered a fictional concept: Perhaps you've seen this term in a book, movie, or game.
* It's a play on words: The term might be a humorous or ironic reference to the county of Sussex in England, playing on the "-ology" suffix commonly used for academic disciplines.
* You might be misremembering: It's possible you're remembering something else related to Sussex and are mistakenly associating it with "Sussexology."
If you can provide more context about where you saw this term, it might be easier to figure out what it actually refers to.