From the French for scamp, and the Middle Dutch for imp, it is a short, sweet and oh, so evocative word. Use it in dialogue and you can immediately characterize both the speaker AND the object of derision (because when someone calls another person "droll" is usually not a "good" thing).
Synonyms: Witty, a clown. Antonyms: serious (or another of my favorite "d" words, DOUR!)
"Oh, my dear boy, do tell us another

See? You know that someone in the scene is seething, right? And that one Duchess is due for a comeuppance .....