"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).
"a tidal river," 1650s; see salt (n. ) + river. as a proper name, it was used early 19c. with reference to backwoods inhabitants of the U.S., especially those of Kentucky (there is a Salt River in the Bluegrass region of the state; the river is not salty, but salt manufactured from salt licks in the area was shipped down the river). The U.S. political slang phrase to row (someone) up Salt River "send (someone) to political defeat" probably owes its origin to this geographical reference, as the first attested use (1828) is in a Kentucky context. The phrase may also refer to the salt of tears.