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," from ex "from, forth" (see ex-) + ponere "to put, place" (see position (n.)). Altered in French 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.