Green’s Dictionary of Slang

(US black) arrogantly.

1880		St Johnsbury Caledonian (VT) 17 Sept. 1/7: Der got ter runnin’ on talkin’ mighty biggity.
1884		J. Harrison ‘Negro English’ in Anglia VII 272: To talk biggity = to talk big, to order.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 213: biggity, sophisticated. ‘You needn’t act so biggity.’.
1934		O. Strange Sudden 149: Fella with a gun can allus talk biggity to the chap what ain’t wearin’ his.
1946		Mezzrow & Wolfe Really the Blues 5: We had a yen, every time we got away from home and school, to strut and act biggity.
1965		C. Brown Manchild in the Promised Land (1969) 100: Mamam never acted biggety in court, but she would bow her head only so low.