Wikipedia
Plain people
Plain people are Christian groups characterized by separation from the world and simple living, including plain dress. Most Plain people have an Anabaptist background with the exception of the Old German Baptist Brethren and Old Order River Brethren. All but the Old Order River Brethren are of German, Swiss German and Dutch ancestry.
Usage examples of "plain people".
This they do not wish, for to plain people things not of earth are unwelcome.