Green’s Dictionary of Slang

1. a general excl. of excitement, pleasure.

1943		advert in L. Bennett Jam. Humour [inside cover] Bwoy what a ting can nice! Tark ’bout nice t’ings? Bwoy . . . a dis one de mad dem! No odder corfie can come near Missa Lascelles’ Blue Mountain – Is a class corfie dat, man – You must know!
1990		L. Goodison Baby Mother and King of Swords 78: Bwoy, Bella a you broader than Broadway.
2000		Guardian Guide 8–14 Jan. 26: The mutha hired Little Mimsie’s Golf club, [...] and the place rocked, bwoy!

2. a general excl. of surprise, disdain.

1981		N. Farki Countryman Karl Black 10: ‘If it don’t . . . ’ he took a deep breath, ‘ah, bwoy!’.
2003		Dizzee Rascal in Vice Mag. at Hyperdub.com 🌐 As I’m going into my music life they’re going into my police life but at a time we were all doing the same thing. So, bwoy, what does that say?