Wonk

The word was used - strictly as a verb - at Harvard in the 1950s, to mean "hunker down for some serious studying," as in "I can't go out tonight. I have to wonk for my chem exam." The folk etymology was that it was KNOW spelled backwards, though how that led to the new meaning was cloudy at best. Though I never encountered it as a noun, I suppose people who did it could have been called wonkers.

I have to wonk for an exam.