- plain (adj.)
- c.1300, "flat, smooth," from O.Fr. plain, from L. planus "flat, even, level" (see plane (1)). Sense of "evident" is from, c.1300; meaning "simple, sincere, ordinary" is recorded from late 14c. In reference to the dress and speech of Quakers, it is recorded from 1827; of Amish and Mennonites, from 1904. Of appearance, as a euphemism for "ill-favored, ugly" it dates from 1749.
- plain (n.)
- "level country," c.1300 (originally in ref. to Salisbury Plain), from O.Fr. plain, from L. planum "level ground, plain," properly neut. of adj. planus "flat, even, level" ((see plane (1)). L. planum was used for "level ground" but much more common was campus. Plains of the American Midwest first so called 1684.