James Reese Europe. Source: wiki.

Long before the “gig economy”, the term gig was widely used in circles such as jazz and WAM. I’m fond of the story about the late lamented Linda Smith chatting with her mum.

The New Grove dictionary of music and musicians gives a succinct, dry definition:

a term commonly applied to a musical engagement of one night’s duration only; to undertake such an engagement.

Wiki elaborates:

Gig is slang for a live musical performance, recording session, or other (usually paid) engagement of a musician or ensemble. Originally coined in the 1920s by jazz musicians, the term, short for the word “engagement” [?], now refers to any aspect of performing such as assisting with performance and attending musical performance. More broadly, the term “gigging” means having paid work, being employed.

More detailed is this discussion on stackexchange, referring to the Word detective site.

I associate the term particularly with freelancers. A Messiah in Scunthorpe for a jolly good tea is a gig of sorts, but so is a Matthew Passion at King’s College Chapel in Cambridge. I wonder when WAM musos, ever keen to deflect pomposity (cf. Viola jokes and maestro-baiting), began using the term.

But (apud Word detective)

Every job is a “gig” today.  Calling your job a “gig” is a way of saying “I’m not really emotionally invested in my job, which I find boring and soulless, and I’m only doing it so I can act/write novels/play jazz saxophone on the weekends”.  And it’s not just laconic “baristas” at Starbucks.  I’ve heard corporate lawyers describe their positions as “gigs”.

Commonly cited is a 1926 Melody maker article, whose byline reads, “One Popular Gig Band Makes Use of a Nicely Printed Booklet”. But The jazz lexicon goes further:

According to jazzman Eubie Blake, bandleader James Reese Europe used the term in its jazz sense as early as c1905; widely current since c1920.

While the use of the term in the jazz world since the early 20th century is widely attested, there are many interesting suggestions about its earlier usage, which remain controversial. The Oxford English dictionary suggests (*Sexism watch!*):

The meaning of the term “gig” is transferred from the deprecatory term for a “flighty girl” and subsequently indicates anything which whirls, or is dangerous or unpredictable.

Word detective has more, alas without giving a source:

The first incarnation of “gig,” around 1225 [?!], was to mean “a flighty, giddy girl,” although this sense may well have been based on an earlier sense of “gig” meaning “something that spins or whirls” (as later found in “whirligig”).  The Oxford English Dictionary suggests that “gig” may be onomatopoeic or “imitative” in origin, meaning that the word itself was meant to suggest something small that whirls.  This sense of “gig” later came to also mean “an odd person, a fool” as well as “a joke” or “a state of boisterous merriment and fun” (“in high gig”).

This sense leads to an etymology from “giggle”, having some fun.

Source: wiki.

By the late 18th century, gig commonly referred to a light, one-horse carriage, popular in New Orleans; by extension,

The thought is that black musicians, in order to avoid being arrested for playing on the street, would instead play jazz on the back of carriages or trucks.

I’m most attracted to two possible musical derivations from gigue (jig), or geiger fiddle. GIG has also been claimed as an acronym: God Is Good, or Get It Going.

Stackexchange thickens the plot bewilderingly by citing the Dictionary of American slang (1960):

gig n. 1 A child’s pacifier or any object, as a cloth square, spoon, or the like, used as a toy; any object to which a small child is attached and with which he likes to play; any object treated by a child as a fetish; a gigi or ju-ju. Orig. Negro slave and Southern use. From “gigi,” the word is very well known to about 35% of the population, unheard of by the rest. 2 [sometimes taboo] The rectum. From “gigi.” Used euphem. by some children, as part of their bathroom vocabulary, but not common to all children. Used by some male adults [taboo] as a euphem. for “ass” in such expressions as “up your gig.” 3 [taboo] The vagina. From “gigi.” Not common. Prob. Southern use. 4 A party, a good time; esp. an uninhibited party; occasionally but not often, an amorous session, necking party, or even a sexual orgy between a man and a woman. c1915 [1954]: “Cornet players used to pawn their instruments when there was a lull in funerals, parades, dances, gigs and picnics.” L. Armstrong, Satchmo, My Life in New Orleans, 100. 1958: “Life is a Many Splendored Gig,” a song title. 5 A jam session ; a jazz party or gathering of jazz musicians or enthusiasts. Orig. swing use. 1920 [1954]: “Kid Ory had some of the finest gigs, especially for the rich white folk.” L. Armstrong, Satchmo, My Life in New Orleans, 141. 6 Specif., an engagement or job for a jazz musician or musicians, esp. for a one-night engagement. 1950: “If I ask you to go out on a gig, it’s thirty-five or forty dollars for that night.” A. Lomax, Mr. Jelly Roll, 204. 1954: “On a gig, or one night stand.” L. Armstrong, Satchmo, My Life in New Orleans, 221. 7 Something, as a jazz arrangement, that is satisfying or seems perfect. Orig. swing use. 8 A fishing spear; a pronged fork as used for catching fish, frogs, and the like. 1946: [citation omitted]. 9 An unfavorable report; a demerit; a reprimand. Army and some student use since c1940. The relations, if, any, between a child’s pacifier or fetish, the rectum and vagina, a party, a sex orgy, jazz music, a pronged fork, and a reprimand are most interesting, and lie in the field of psychology rather than of etymology.