"member of the lowest class," 1530s, from Latin plebius "person not of noble rank," from adjective meaning "of the common people" (see plebeian, adj.).

also plebian, "of or characteristic of the lower class," 1560s in a Roman historical sense, from Latin plebeius "belonging to the plebs," earlier plebes, "the populace, the common people" (as opposed to patricians, etc.), also "commonality; the mass, the multitude; the lower class," from PIE *ple- (see pleio-). In general (non-historical) use from 1580s.