Origin and history of salty

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 1910 (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."

"quality or condition of being salt," 1660s, from salty + -ness. Earlier was simply saltness, from Old English sealtnes.