A Wonk is some kind of expert, who spends too much time studying something or other. Wonk can mean "WithOut Normal Knowledge" or it can simply be, "know" spelt backwards. It's also beeen suggested that it comes from a British word, "Wonky" meaning unsteady or unsound. They've even suggested that wonk has something to do with "wank". "Since slang is often born on the gritty streets of language rather than in the language lab, its origins are often hard to pin down."
The English language wonks can't agree on the origin of the word.