Incense means both "to make angry" and a stick that burns slowly and emits a strong smell. If your new college roommate burns incense in your tiny dorm room, you might get incensed and storm out.
How can a word that means a substance that is burned for its sweet odor come to mean "make very angry"? Both have to do with the idea of burning, and the Latin root incendere, "to set on fire." A stick of incense must be lit, or set on fire to release its smell. When you are incensed by something, such as your teacher slamming you with homework on the night of the prom, you feel like you are burning with anger.