Gig
late 18th century: apparently a transferred sense of obsolete gig ‘a flighty girl’, which was also applied to various objects or devices that whirled.
wiktionary
Of uncertain origin. Some theories pose its origin in Middle English gige(“fiddle”) or Middle English *gygge (found in Middle English whyrlegygge(“a top, whirligig, a rotating device”)), akin to Old Norse gígja(“fiddle”) and German Geige(“violin”). In Irish, the word gíog is an onomatopoeia meaning "chirp, tweet, squeak". However, none offers established continuity with the present sense. The earliest usage of the word gig in the sense of “any, usual temporary, paid job” found by linguist Geoffrey Nunberg is from a 1952 piece by Jack Kerouac about his gig as a part-time brakeman for the Southern Pacific railroad. [1]
Clipping of giga-, as in gigabyte, gigaunit, etc.
From Middle English gigge, from Old French gigues(“a gay, lively girl”), from Old Norse gikkr(“a pert person”), related to Danish gjæk(“a fool; jester”), Swedish gäck(“a fool; jester; wag”). More at geck.
etymonline
gig (n.1)
"light, two-wheeled carriage, usually drawn by one horse" (1791), also "small boat," 1790, perhaps imitative of bouncing. There was a Middle English ghyg "spinning top" (in whyrlegyg, mid-15c.), also "giddy girl" (early 13c., also giglet), from Old Norse geiga "turn sideways," or Danish gig "spinning top." Similar to words in continental Germanic for "fiddle" (such as German Geige); the connecting sense might be "rapid or whirling motion."
gig (n.2)
"job," originally in the argot of jazz musicians, attested from 1915 but said to have been in use c. 1905; of uncertain origin. As a verb, by 1939. Among the earlier meanings of gig was "combination of numbers in betting games" (1847). Gig-economy is attested from 2009. Related: Gigged; gigging.
