Villanus referred to a worker attached to a country estate. Through French vilain, a class-based description became an insult. English eventually sharpened the insult into wickedness, and later applied it to the antagonist in a story.
Sources
- Merriam-Webster · villain
Dictionary word history; the component and historical references below supply additional detail.
- Online Etymology Dictionary · villain
Historical forms, meanings, and context for the route described here.