villein (n.)

early 14c., vileyn, spelling variant of villain in its reference to a feudal class of half-free peasants. It tends to keep the literal, historical sense of the word and let the pejorative meanings go with villain; Century Dictionary writes that "the forms villain, villein, etc., are historically one, and the attempt to differentiate them in meaning is idle," but Fowler finds this "a useful piece of differentiation." Related: Villeinage.