Lots of words. And some I'd never get to use outside of gaming - verisimilitude, for example, or gestalt.
I learned a lot when writing Artificer's Handbook. For example, the vikings used a gem called iolite as a rudimentary compass, because it has a special property that reflects light a certain way if it's position is stable, thus you can tell the precise location in the sky with an iolite gem. Weird stuff like that. Or that the corpse flower is an enourmous flower that only grows in one place in the world naturally, is like 5 feet in diameter (it's actually thousands of small flowers combined) and smells like rotting corposes. It also only blooms like once every 14 years or something like that.