Green’s Dictionary of Slang

1. a boaster, a braggart.

1932		J. Peterkin Bright Skin 76: Nobody couldn’ dominize dat gal. E was big doins up to de last breath e drawed. E didn’ have no shame.
1970		in DARE.
1994		(ref. to 1900s–20s) C. Major Juba to Jive 33: Big do; big doing (1900s–1920s) any unusually exciting or frenzied event; a pompous person; a show-off; a bully.

2. any notable event, esp. a party or celebration.

1894		M.H. Foote Coeur d’Alene 88: Big doin’s to-night, eh? The old man puts on a heap of dog.
1902		Akron Dly Democrat (OH) 8 Nov. 7/2: Several large factories are projected — Don’t be surprised if your [sic] surprised by ‘BIG DOIN’S’ along this Belt Ry. in the near future.
1908		K. McGaffey Sorrows of a Show Girl Ch. vii: One of the young ladies inadvertently remarked that there was to be big doings at a nearby hall.
1913		J. London Valley of the Moon (1914) 58: You an’ me’s goin’ acrost to Frisco Friday night. There’s goin’ to be big doin’s with the Horseshoers.
1921		Topeka State Jrnl (KS) 12 Sept. 9/2: The big Free Fair [...] the big doin’s is the annual frolic of Kansas.
1932		in DARE.
1952		W.R. Burnett Little Men, Big World 166: Big doings—and he was in on it.
1994		see sense 1.