early 15c., "to leave without shelter or defense," from Middle French exposer "lay open, set forth" (13c.), from Latin exponere "set forth" (see expound), altered by confusion with poser "to place, lay down" (see pose (v.1)). Meaning "to exhibit openly" is from 1620s; that of "to unmask" is from 1690s. Photographic sense is from 1839. Related: Exposed; exposes; exposing.
also exposé, "display of discreditable information," 1803, initially as a French word; past participle of French exposer (see expose (v.)). Earliest use was in reference to Napoleon.