1590s, "a sending abroad" (as an agent), originally of Jesuits, from Latin missionem (nominative missio) "act of sending, a dispatching; a release, a setting at liberty; discharge from service, dismissal," noun of action from past-participle stem of mittere "to release, let go; send, throw," which de Vaan traces to a PIE *m(e)ith- "to exchange, remove," also source of Sanskrit methete, mimetha "to become hostile, quarrel," Gothic in-maidjan "to change;" he writes, "From original 'exchange', the meaning developed to 'give, bestow' ... and 'let go, send'."
Meaning "an organized effort for the spread of religion or for enlightenment of a community" is by 1640s; that of "a missionary post or station" is by 1769. The diplomatic sense of "body of persons sent to a foreign land on commercial or political business" is from 1620s; in American English, sometimes "a foreign legation or embassy, the office of a foreign envoy" (1805).
General sense of "that for which one is sent or commissioned" is from 1670s; meaning "that for which a person or thing is destined" (as in man on a mission, one's mission in life) is by 1805. Meaning "dispatch of an aircraft on a military operation" (by 1929, American English) was extended to spacecraft flights (1962), hence, mission control "team on the ground responsible for directing a spacecraft and its crew" (1964). As a style of furniture, said to be imitative of furniture in the buildings of original Spanish missions to western North America, it is attested from 1900.
"relating to or pertaining to a mission, sent on a mission," especially a Christian mission, 1640s, from Modern Latin missionarius "pertaining to a mission," from Latin missionem (see mission).
also peacekeeping, 1961 in the international sense, "regular maintenance by an organization of peace between nations or communities," from peace + keeping, verbal noun from keep (v.). Earlier "preservation of law and order" (mid-15c.), from verbal phrase keep the peace. Related: Peace-keeper (1570s).
c. 1400, "mission of a deputy or envoy," from Old French legation "embassy, mission" and directly from Latin legationem (nominative legatio) "the office of an ambassador," noun of action from past participle stem of legare "send as a deputy" (see legate). From c. 1600 as "body of deputies sent, representatives," 1832 as "official residence of a diplomat."
"person sent on a mission," 1620s, from French émissaire (17c.) or directly from Latin emissarius "a scout, a spy," literally "that is sent out," from emissus, past participle of emittere "send forth" (see emit).
"the entire scenery and properties of a stage play," 1830, from French mise en scène, literally "setting on the stage," from mise (13c.) "a putting, placing," noun use of fem. past participle of mettre "to put, place," from Latin mittere "to send" (see mission). Hence, figuratively, "the surroundings of an event" (1872).