Green’s Dictionary of Slang

1. (orig. US black, also bro-bro, bronem) a brother, whether lit. or fig. (cf. bra n.).

1762		Bridges Homer Travestie (1764) I 202: My dearest bro. for this did I / Desire a truce, zounds! I could cry.
1772		Bridges Burlesque Homer (3rd edn) 473: His bro. was pretty near.
1797		Bridges Burlesque Homer (4th edn) II 313: [as cit. 1772].
1922		M.E. Smith Adventures of a Boomer Op. 93: He’d never say ‘No’ to a wandering Bro’ / Who asked him for a meal.
1940		J.H. O’Hara Pal Joey 30: Betty said her bro.-in-law never went to night clubs.
1940		M. Marples Public School Slang 133: The young ’un was once the correct designation for a young brother, but the modern equivalent is possibly my bro.
1953		S. Bellow Augie March (1996) 81: This kid is a buddy of mine and he works for my bro.
1965		J.P. Carstairs Concrete Kimono 169: I say, are you going to marry my bro’?
1970		Current Sl. V:2.
1979		M. Matshoba ‘Son of the First Generation’ Call Me Not A Man 66: Bro Zakes raised his eyebrows dumbfoundedly.
1986		T. Philbin Under Cover 201: That’s my bro, baby. Serious guy.
1994		J. O’Connor Secret World of the Irish Male (1995) 591: ‘No,’ says the bro.
2002		J. Cameron Hell on Hoe Street 208: And what about me and my bro here.
2011		Times Mag. 30 Apr. 14/3: Bros before hos.
2018-20		T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Bro - friend, associate, may also be used for a biological sibling.
2019		N. Walker Cherry 150: Several bros would ride in the Fuck Van and they’d be on the lookout. Then one bro would go ‘look’ and he’d point out a young woman.
2020		G. Armstrong Young Team 10: [M]a big bro’s been roon the block a few times.
2021		Central Cee ‘6 for 6’ 🎵 Told bro-bro that you gotta' take it slow / But he knows crime pays, so he won't go lidge’.

2. as a term, of address, esp. between blacks.

1926		Frankie ‘Half-Pint’ Jaxon ‘Hannah Fell in Love with my Piano’ 🎵 You gonna put it in my stocking, the money, bro?
1957		H. Simmons Corner Boy 132: ‘Keep the change.’ [...] ‘Thanks, bro.’.
1967		P. Thomas Down These Mean Streets (1970) 104: We waited some more and a colored cat came down. ‘Hey, bruh,’ I called.
1968		N. Heard Howard Street 77: What you been doin’ for yourself, little bro?
1975		D. Goines Inner City Hoodlum 109: I dig where you’re comin’ from, bro.
1980		J.L. Gwaltney Drylongso 284: But, Bruh’ John, it is an advanced age for a person with sickle-cell anemia.
1981		A. Weller Day of the Dog 63: No worries, broh.
1985		T.R. Houser Central Sl. 12: brough [...] ‘Say, brough, wha’s uh’.
1985		J. Wambaugh Secrets of Harry Bright (1986) 44: Where’s da money, bro?
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Bro. A form of address denoting friendship or affection. Contraction of brother. More frequently used by aboriginal prisoners.
1997		G. Sikes 8 Ball Chicks (1998) 197: [to a woman] You scared the shit out of me, bro.
1999		Observer Rev. 20 June 16: The sight of more public schoolboys addressing each other as ‘bro’ might just make you want to smash their heads in.
2003		McGill Reed Dict. of N.Z. Sl. 34: bro Greeting, particularly popular among Maori, short for ‘brother’, imported from the Black Brothers in America. Maori gangs are identified generally as The Bros and hospitals in some areas are known as Bro-repairs, a play on the Beaurepaires tyre retailing chain.
2004		C. Brookmyre Be My Enemy 98: How’s it going, bro?
2010		A. Steinberg Running the Books 6: Inmates exchange intrixcate handshakes and formal titles: OG, young G, boo, bro, baby boy, brutha, dude, cuz, dawg, P, G, daddy, pimpin’, nigga, man, thug thizzle, my boy, my man, homie.
2012		J. Díaz This Is How You Lose Her 97: Bro, you’re working at the Yarn Barn!
2016		A. Wheatle Crongton Knights 6: ‘Calm down, bro’.
2021		T. Swerdlow Straight Dope [ebook] Hey bro, let me get a word with you.

3. (also bronem, bru) a black male, abbr. brother n. (2)

1968		‘Sl. of Watts’ in Current Sl. III:2 11: Bro, n. Short for brother, fellow Negro.
1982		(con. 1970) J.M. Del Vecchio 13th Valley (1983) 33: Gradually he went from being valled L-T B to L-T Bro.
1982		W. Safire What’s The Good Word? 84: A box being one of those big portable radio/cassette players the bros carry around.
1991		B. Hamper Rivethead (1992) 53: You just didn’t find too many bro’s hangin’ around the communion rail.
2010		Mail & Guardian (Johannesburg) 8 Jan. 🌐 Totsiens, bru.
2021		Central Cee ‘Xmas Eve’ 🎵 My lil’ bronem see me with P, on G and now they wan’ trap like me.

4. (N.Z. prison) pl., constr. with the anyone dark-skinned, usu. M?oris or Pacific islanders.

1999		D. Looser ‘Boob Jargon’ in NZEJ 13 36: the bros n. Dark-skinned people, (esp. Maoris).
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 31/1: bros, the n. pI. 1 dark-skinned people, esp. Maori or Pacific Islanders.

5. (N.Z. prison) pl., constr. with the one’s inmate peer group.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 31/1: bros, the n. pI 2 one's fellow prison inmates.

6. (US campus) orig. a member of a fraternity; also used as adj. meaning athletic, sporty; by 1970s the use developed to mean a male friend and the hedonistic lifestyle pursued (see https://en.wikipedia.org/wiki/Bro_culture); thus v. bro to act in a manner typical of such individuals.

2012		C. Eble (ed.) UNC-CH Campus Sl. 2011 2: BRO [...] Member of a social fraternity: ‘Those bros took up a whole row at the football game.’ Athlete, athletic: ‘That guy is pretty bro.’.
2012		M. Lacher On the Bro’d 44: Derek is getting all pussywhipped by these chicks and can’t bro it as hard as we want.