When the word "reify" popped up recently on a "Word of the Day" application I have, I was sure I could guess the definition. I knew what "deify" (from Latin deus, god) meant, and I thought for certain that "reify" must be from Latin rex, king---and thus probably meant "to crown as king" or "to treat as a king".
Actually, the root is not rex but res, a delightful word whose brevity belies its multitude of meanings. I learned its translation in first-year Latin as "thing, matter, or affair" but never really understood it until I encountered it in contexts like res publica or in medias res. And so, in fact, "reify" has nothing to do with kings but means "to convert into or regard as a concrete thing, e.g. to reify a concept".
Incidentally, the above-mentioned application from Merriam-Webster is pretty cool. It not only gives you a word's definition, but also a sample sentence and an interesting fact. Even when I'm already familiar with the word of the day, I usually end up learning something.