ヴィラ、村、農場が語源。本来の意味は村人だが、蔑称として悪党、悪党と訳されるようになった。
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.