1796, "elevated tract of relatively level land," from Fr. plateau,
from O.Fr. platel
(12c.) "flat piece of metal, wood, etc.," dim. of plat
"flat surface or thing," noun use of adj. plat
). Meaning "stage at which no progress is apparent" is attested from 1897, originally in psychology of learning. The verb is attested from 1952, from the noun.