The word "demure" describes a person, typically a woman, who is modest, reserved, and shy in behavior or appearance. It implies a certain level of decorum and can suggest an innocent or gentle quality, often in contrast to being bold or flashy.
The word "demure" comes from the Middle English "demure," which means "mature" or "serious." This, in turn, is derived from the Old French "demourer," meaning "to remain" or "to stay," and is related to the word "demeanor." The sense of being modest or reserved developed over time.