The Random House Dictionary of Historical American Slang1996, v.I, pp 890-891, gives detailed definitions with examples of usage for the word "gig", (1.5 pages very small print, very big pages. too much to post) in general chronological order of their appearance:

1. the vagina [orig. unkn] 1698-99
2. the anus [Cf] giggy, children bathroom and adults eupehm for "ass" ie up your n. 1954-60
3. two wheeled, one horse carriage
4. in policy gambling a set of usu. three number played by a better 1847
5. an instance of goading, gibing, or reproving 1901
6. a business affair, state of affairs, undertaking or event 1907
7. a job, an occupation 1908
8. ones preference or special interest 1965
9. an engagement, esp. for a single evening. to perform jazz, rock. or other popular music1926
10. a criminal undertaking, job 1953
11. an eye 1924
12. gigolo 1926
13. to cheat, take dishonest advantage of 1914
14. to place on disciplinary report; administer official punishment 1930
15. Orig Jazz to play single engagements as a jazz musician or (later) other entertainer (hence) to have employment 1939
16. to provide employment for 1971

Personal notes: Surprised at the French #1-2 (I thought it was only the Greeks) that confused a vagina and an anus.

Texas A&M uses the expression "Gig em' Aggies" at football games….their use is derived from the military heritage…..ie. unpolished shoes, or an un-buttoned button is a "gig-point." aka demerit, black-mark.

BTW --- WW --- I have wonderful memories of the Santa Fe Opera (before enclosure) and a "Flying Dutchman" performance, the natural elements added their own spectacular effects with wind, lightning, lots of lightning, and a little rain.