Green’s Dictionary of Slang

1. to make advances, to court.

1832		Polit. Examiner 8 Dec. 4/1: I seed her at church one day fixed up kinder pretty snug; so [...] darn my seelskin pumps if I dont buck up to her next Fust day [DA].
1856		Yorkville Enquirer (SC) 14 Feb. 4/3: ‘I heard you were bbucking up to the widow’.
1858		A. Mayhew Paved with Gold 229: Begad, Tom [...] I shall have to get you to buck up to the old girl, and carry her off.
1868		J.K. Paulding Book of Vagaries 265: Single gentlemen [...] should beware how they ‘buck up to widows’ [DA].
1895		Oxford Public Ledger (NC) 18 Jan. 1/3: The crowd they have been bucking up to for revenue have become regular old begro loving Republicans.
1903		J. Furphy Such is Life 14: Well, this ole beggar he’s buckin’ up to Miss King, the governess, an’ Moriarty, the storekeeper, he’s buckin’ up to her too.
c.1905		J. Furphy Rigby’s Romance (1921) Ch. xxx: 🌐 Tried to buck up to another girl, purpose to vex Nora.

2. to defy, to rebel against, to stand up to.

1847		W.T. Porter Quarter Race in Kentucky 45: I never paid no ’tention to him, till he bucked up too [sic] me an give me a feller rite under the ear.
1895		Wichita Dly Eagle (KS) 20 Apr. 4/1: Nicaragua is bucking up to England in gallant style.
1909		DN III 409: Buck up [...] To rebel.
1912		DN III 572: Buck up [...] To stand up manfully; to meet one squarely. ‘Don’t be afraid; buck right up to him.’.
1942		(con. 1900–18) F. Warnick Dialect of Garrett County, Maryland 4: Buck up to [DARE] .
1957		AS XXXII: 285: To buck up to somebody means to talk and act as good or big as that somebody.