Green’s Dictionary of Slang

1. a nickname for the BMW motorcar, esp. popular as a status symbol and as a target for theft; various ‘translations’ of BMW include ‘black man’s wheels’, ‘black man’s wagon’, ‘Bob Marley and the Wailers’, ‘break my windows’. The actual name comes from that of the German manufacturer, Bayerische Motor Werke.

1983		T. White Catch a Fire 276: Pulling onto the Island House grounds in the silver BMW (‘Lettars stand fe Bob Marley an’ Wailars’).
1993		S. King Dolores Claiborne 149: Sometimes their brakes fail and they run their BMWs into oak trees.
1994		C. Major Juba to Jive 50: BMW (1990s) stands for ‘break my windows.’ BMW [...] cars are a type often burglarized.
1999		J. Cameron Brown Bread in Wengen [ebook] TT got a BMW. Reckoned he was a black geezer maybe, Black Man’s Wheels.

2. (US black) black man working [apparently based on the ‘luxury’ of finding a job if black].

1994

G. Smitherman Black Talk 64: BMW Black man working. The abbreviation and the expression signify on racism and the economic discrimination that result in overwhelming numbers of African American men being unemployed; thus, one working is a valuable luxury, like the BMW automobile.

3. (S.Afr. gay) be my wife, an invitation to have sexual intercourse.

2003

K. Cage Gayle 55/1: BMW (abbr.) an invitation to indulge in sexual intercourse [abbr. of Be My Wife].

4. (S.Afr.) black man’s wish.

2005

Marie Clare (UK) Jan. 81: You have to listen to the joke that circulates in the townships: ‘What is a BMW?’ ‘A Black man’s wish.’.