Lil Jay, a gang member from the St Lawrence Boys set of the Insane Gangster Disciples, said “Die Ls for Lamron” in the intro of his song “Who the F*ck is Dude”. Lamron is at war with the St Lawrence Boys gang, therefore it’s common to hear both sides say Die L’s for the other gang. Die Ls can also be spelled Die Lz, it’s a slang term, and can be spelled however you want.
The die L’s symbol is made by making an L shape using your thumb and your index finger, and then turning it upside down as shown in the picture in this page. In many rap videos of rappers whom are in gangs, they often do the die L’s symbol, which often looks as if they are pointing to the ground to those unfamiliar with its meaning. The opposite of Die L’s is “L’s Up”.