Green’s Dictionary of Slang

1. (orig. US) to become friendly, to live or travel as friends.

1919		in A. Wallgren AEF in Cartoons (1933) [caption] I always wanted to buddie up with an officer .
1930		L. Johnson ‘On the Wall’ 🎵 Now then, now you ain’t good looking and you don’t dress fine /Just kind treatment make me buddy you ‘most any old time.
1931		Irwin Amer. Tramp and Und. Sl. 224: Many tramps will ‘buddy up’ and travel together for years.
1948		(con. 1944) N. Mailer Naked and Dead 456: A platoon leader didn’t buddy.
1948		N. Algren ‘The Heroes’ in Lehmann Penguin New Writing No. 34 137: My cot was next to his, and we started buddying up.
1952		J. Jones From Here to Eternity (1998) 82: He buddies around with Sgt Henderson.
1952		Lait & Mortimer USA Confidential 120: Frank also buddied with the Chinese.
1956		H. Gold Man Who Was Not With It (1965) 96: You think you’re going to buddy up with me?
1967		F. Salas Tattoo the Wicked Cross (1981) 60: We’ll get to buddy up all the time we’re here.
1978		R. Price Ladies’ Man (1985) 237: Like a sixties liberal buddying up to a yom.
1986		L. Heinemann Paco’s Story (1987) 154: They would always wind up buddied up to the platoon shithead.
1993		T. Jones Pugilist at Rest 62: We can buddy up.
2000		C. Cook Robbers (2001) 29: They’d buddied up just that fast, that easy.

2. (orig. US) to ingratiate oneself, to curry favour with someone.

1950		B. Rose 13 Jan. [synd. col.] The wisdom of buddying up to Franco of Spain [W&F].
1958		E. Wilson 16 Feb. [synd. col.] He’s hanging out with Walson now and buddying up to him [W&F].
2001		J. Stahl Plainclothes Naked (2002) 140: Nothing enraged an abusee like having some male cop buddy up to her dickwad boyfriend or husband.