Middle English had a verb getten, jetten meaning "to prance, strut, swagger, be showy" (c. 1400), from getter, jetter, the Old French form of the verb. Related: Jetted; jetting.
1690s, "stream of water," from French jet "a throw, a cast; a gush, spurt (of water); a shoot (of a plant)," from jeter "to throw, thrust" (from PIE root *ye- "to throw, impel"). Middle English had jet/get "a device, mode, manner, fashion, style" (early 14c.).
Sense of "spout or nozzle for emitting water, gas, fuel, etc." is from 1825. Hence jet propulsion (1855, originally in reference to water) and the noun meaning "airplane driven by jet propulsion" (1944, from jet engine, 1943). The first one in service was the German Messerschmitt Me 262. Jet set first attested 1951, shortly before jet commuter plane flights began. Jet age is attested from 1952. The atmospheric jet stream is from 1947.
1900, coined by U.S. author L. Frank Baum (1856-1919) in "The Wonderful Wizard of Oz." He never explained how he got the word.
The word most like it is perhaps mutchkin, an old Scottish measure of capacity for liquids, which was used by Scott. (It comes from Middle Dutch mutseken, originally "a little cap," from mutse "cap," earlier almutse "amice, hood, headdress," from Latin amictus "mantle, cloak," noun use of past participle of amicire "to wrap, throw around," a compound from ambi- "around" (see ambi-) + iacere "to throw" (see jet (v.)).
But some Baum scholars see a possible inspiration in Münchner Kindl, the name of the emblem of the city of Munich (German München) or in German Männchen, literally "little man," which is cognate with mannequin.
While she stood looking at the strange and beautiful sights, she noticed coming toward her a group of the queerest people she had ever seen. They were not as big as the grown folk she had always been used to; but neither were they very small. In fact, they seemed about as tall as Dorothy, who was a well-grown child for her age, although they were, so far as looks go, many years older. ["The Wonderful Wizard of Oz"]
also sea-coal, old name for "mineral coal, fossil coal" (as opposed to charcoal), late 13c., secol; earlier, in Old English, it meant "jet," which chiefly was found washed ashore by the sea. See sea + coal (n.). The coal perhaps was so called for its resemblance to jet, or because it was first dug from beds exposed by wave erosion. As it became the predominant type used, the prefix was dropped.