early 15c., "to leave without shelter or defense," from Old French esposer, exposer "lay open, set forth, speak one's mind, explain" (13c.), from Latin exponere "set forth, lay open, exhibit, reveal, publish" (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; noun use of past participle of French exposer "lay open" (see expose (v.)). Earliest use was in reference to Napoleon.