villain (n.)
c.1300 (late 12c. as a surname), "base or low-born rustic," from Anglo-French and Old French vilain "peasant, farmer, commoner, churl, yokel" (12c.), from Medieval Latin villanus "farmhand," from Latin villa "country house, farm" (see villa).
The most important phases of the sense development of this word may be summed up as follows: 'inhabitant of a farm; peasant; churl, boor; clown; miser; knave, scoundrel.' Today both Fr. vilain and Eng. villain are used only in a pejorative sense. [Klein]
Meaning "character in a novel, play, etc. whose evil motives or actions help drive the plot" is from 1822.