salt river n.

Old English sealt "salt, sodium chloride, abundant substance essential to life, used as a condiment and meat preservative," from Proto-Germanic *saltom (source also of Old Saxon, Old Norse, Old Frisian, Gothic salt, Dutch zout, German Salz), from PIE root *sal- "salt."

Applied from early 14c. to various substances resembling common salt. Modern chemistry sense "compound of an acid radical with a base radical" is from 1790; as an ultimate element in alchemy from 1580s. Meaning "experienced sailor" is attested by 1840 (Dana), probably a reference to the salinity of the sea. By 1570s as "that which gives piquancy to discourse or writing or liveliness to a person's character."

Salt long was regarded as having power to repel spiritual and magical evil. Many metaphoric uses reflect that this was once a rare and important resource, such as worth one's salt "efficient, capable" (1830), salt of the earth "persons of worthiness" (Old English, after Matthew v.13). Belief that spilling salt brings bad luck is attested from 16c. To be above (or below) the salt (1590s) refers to customs of seating at a long table according to rank or honor, and placing a large salt-cellar in the middle of the dining table.

Salt-shaker is from 1882. Salt-and-pepper (adj.) "of dark and light color" is by 1915 (pepper-and-salt, 1774, was an old name for a kind of cloth made from dark and light colored wools woven together). To take something with a grain of salt "accept with a certain amount of reserve" is from 1640s, from Modern Latin cum grano salis. The notion is perhaps "modification," hence "allowance, abatement, reserve."

early 13c. (late 12c. in surnames), "a considerable body of water flowing with perceptible current in a definite course or channel," from Anglo-French rivere, Old French riviere "river, riverside, river bank" (12c.), from Vulgar Latin *riparia "riverbank, seashore, river" (source also of Spanish ribera, Italian riviera), noun use of fem. of Latin riparius "of a riverbank" (see riparian).

The generalized sense of "a copious flow" of anything is from late 14c., as is figurative use. The Old English word was ea "river," cognate with Gothic ahwa, Latin aqua (see aqua-). Romanic cognate words tend to retain the sense "river bank" as the main one, or else the secondary Latin sense "coast of the sea" (compare Riviera). In printing by 1898: "streaks of white space in text caused by the spaces between words in several lines happening to fall one almost below the other."

U.S. slang phrase up the river "in prison" (1891) is said to be originally in reference to Sing Sing prison, up the Hudson River from New York City. The phrase down the river "done for, finished" (1893) perhaps echoes the sense in sell down the river (1836, American English), originally of slaves sold from the Upper South to the harsher plantations of the Deep South.

Middle English shit "diarrhea," from Old English scitte "purging, diarrhea," from source of shit (v.). The general sense of "excrement" dates from 1580s (Old English had scytel, Middle English shitel for "dung, excrement;" the usual 14c. noun for natural discharges of the bodies of men or beasts seems to have been turd or filth). As an exclamation attested in print by 1920 but certainly older. Use for "obnoxious person" is by 1508; meaning "misfortune, trouble" is attested from 1937.

Shit-faced "drunk" is 1960s student slang; shit list is from 1942. Shit-hole is by 1937 as "rectum," by 1969 in reference to undesirable locations. Shitload (also shit-load) for "a great many" is by 1970. Shitticism is Robert Frost's word for scatological writing.  

Up shit creek "in trouble" is by 1868 in a South Carolina context (compare the metaphoric salt river, of which it perhaps a coarse variant). Slang not give a shit "not care" is by 1922. Pessimistic expression same shit different day is attested by 1989. To get (one's) shit together "manage ones affairs" is by 1969. Emphatic shit out of luck is by 1942.

The expression when the shit hits the fan "alluding to a moment of crisis or its disastrous consequences" [OED] is attested by 1967.

The expression is related to, and may well derive from, an old joke. A man in a crowded bar needed to defecate but couldn't find a bathroom, so he went upstairs and used a hole in the floor. Returning, he found everyone had gone except the bartender, who was cowering behind the bar. When the man asked what had happened, the bartender replied, 'Where were you when the shit hit the fan?' [Hugh Rawson, "Wicked Words," 1989]