Green’s Dictionary of Slang

(orig. US black/teen) baby gangster, one who is a member of a gang, but has yet to shoot or kill anyone.

1992		St. Louis Post-Dispatch (MO) 2 June 6A/3: BG — Baby gangster.
1998		Mayor’s Anti-Gang Office City of Houston, TX Street Gang Sl. / Gloss. 9 Nov.: b.g. or baby g Term for a very young gangster, approximately 9–12 years old; Stands for ‘Baby Gangster.’.
2001		(con. 1990s) in J. Miller One of the Guys 112: ‘They don’t even sell dope for real, little BGs out here selling for them’.
2002		Ben Davis posting 3 Apr. at Packing.org 🌐 The problems with BG’s in general is that they have no sense of fairness or honor. [...] If the BG, drops his club, throws his hands up in the air and says ‘I give up’ in the .5 second its going to take me to draw and get a bead on his COM, then OK, I have to stop.