The phrase is derived from the slang word "trap," which refers to a place where drugs are sold illegally. In the context of rap songs, "trap" can also be used to refer to the music genre that originated in the trap houses of Atlanta, which is known for its heavy use of synthesizers, hi-hats, and snare drums.
"Die" in this context refers to the possibility of being killed or seriously injured as a result of living a life of crime. It is a reminder that the choices made by the characters in rap songs often have life-or-death consequences.
Overall, the phrase "trap or die" serves to emphasize the high stakes and potential dangers associated with the music industry and the life of crime it often glorifies.