gadgetyoudaoicibaDictYouDict[gadget 词源字典]
gadget: [19] Gadget is an elusive sort of word, as vague in its history as it is unspecific in its meaning. It seems to have originated as a piece of sailors’ slang, and is said to have been current as long ago as the 1850s, but the earliest record of it in print is from 1886, in R Brown’s Spun Yarn and Spindrift: ‘Then the names of all the other things on board a ship! I don’t know half of them yet; even the sailors forget at times, and if the exact name of anything they want happens to slip from their memory, they call it a chickenfixing, or a gadjet, or a gill-guy, or a timmeynoggy, or a wim-wom – just pro tem., you know’.

As for its source, suggestions have included French gâchette ‘catch of a mechanism’ and French dialect gagée ‘tool’.
[gadget etymology, gadget origin, 英语词源]
ratchet (n.)youdaoicibaDictYouDict
1650s, rochet, from French rochet "bobbin, spindle," from Italian rocchetto "spool, ratchet," diminutive of rocca "distaff," possibly from a Germanic source (compare Old High German rocko "distaff," Old Norse rokkr), from Proto-Germanic *rukka-, from PIE root *ruk- "fabric, spun yarn." Compare rocket (n.2). Current spelling in English dates from 1721, influenced by synonymous ratch, which perhaps is borrowed from German Rätsche "ratchet."
rocket (n.2)youdaoicibaDictYouDict
type of self-propelling projectile, 1610s, from Italian rocchetto "a rocket," literally "a bobbin," diminutive of rocca "a distaff," so called because of cylindrical shape. The Italian word probably is from a Germanic source (compare Old High German rocko "distaff," Old Norse rokkr), from Proto-Germanic *rukkon-, from PIE root *rug- "fabric, spun yarn."

Originally "fireworks rocket," meaning "device propelled by a rocket engine" first recorded 1919; rocket-ship in the modern sense first attested February 1927 ("Popular Science"); earlier as a type of naval warship firing projectiles. Rocket science in the figurative sense of "difficult, complex process or topic" is attested by 1985. Rocket scientist is from 1952.
That such a feat is considered within the range of possibility is evidenced by the activities of scientists in Europe as well as in America. Two of them, Prof. Herman Oberth and Dr. Franz Hoeff, of Vienna, are constructing a five-ton rocket ship in which they hope to reach the moon in two days. ["Popular Science," Feb. 1927]