"tedious and ineffectual person," 1935, American English carnival slang, of uncertain origin. Perhaps from jerkwater "petty, inferior, insignificant" [Barnhart, OED]; alternatively from, or influenced by, verbal phrase jerk off "masturbate" [Rawson]. The lyric in "Big Rock Candy Mountain," sometimes offered as evidence of earlier use, apparently is "Where they hung the Turk [not jerk] that invented work."
A soda-jerk (1915; soda-jerker is from 1883) is so called for the pulling motion required to work the taps.
The SODA-FOUNTAIN CLERK
Consider now the meek and humble soda-fountain clerk,
Who draweth off the moistened air with nimble turn and jerk,
[etc., Bulletin of Pharmacy, August, 1902]
"hard silicon dioxide," 1801, Modern Latin, from Latin silex (genitive silicis) "flint, pebble," on model of alumina, soda.
apparently an early Middle English merger of three related Old English nouns, flota "boat, fleet," flote "troop, flock," flot "body of water, sea;" all from the source of float (v.). The early senses were the now-mostly-obsolete ones of the Old English words: "state of floating" (early 12c.), "swimming" (mid-13c.); "a fleet of ships; a company or troop" (c. 1300); "a stream, river" (early 14c.). From c. 1300 as an attachment for buoyancy on a fishing line or net; early 14c. as "raft." Meaning "platform on wheels used for displays in parades, etc." is from 1888, probably from earlier sense of "flat-bottomed boat" (1550s). As a type of fountain drink, by 1915.
Float.—An ade upon the top of which is floated a layer of grape juice, ginger ale, or in some cases a disher of fruit sherbet or ice cream. In the latter case it would be known as a "sherbet float" or an "ice-cream float." ["The Dispenser's Formulary: Or, Soda Water Guide," New York, 1915]
Few soda water dispensers know what is meant by a "Float Ice Cream Soda." This is not strange since the term is a coined one. By a "float ice cream soda" is meant a soda with the ice cream floating on top, thus making a most inviting appearance and impressing the customer that you are liberal with your ice cream, when you are not really giving any more than the fellow that mixes his ice cream "out of sight." [The Spatula, Boston, July, 1908]
c. 1400, "native sodium carbonate" (a sense now obsolete), from Old French nitre (13c.), from Latin nitrum, from Greek nitron, which is possibly of Eastern origin (compare Hebrew nether "carbonate of soda;" Egyptian ntr). Originally a word for native soda, but also associated since the Middle Ages with saltpeter (potassium nitrate) for obscure reasons; this became the predominant sense by late 16c.
1736, "water or liquid thrown upon anything," from splash (v.). Meaning "striking or ostentatious display" is first attested 1804. Sense of "small quantity of soda water, etc., added to a drink" is from 1922. Of color or light, 1832.
late 14c., name given to several useful minerals, specifically to a salt formed from the union of boracic acid and soda, from Anglo-French boras, from Medieval Latin baurach, from Arabic buraq, applied by the Arabs to various substances used as fluxes, probably from Persian burah. Originally obtained in Europe from the beds of salt lakes in Tibet. Related: Boracic.