there are all kinds of slang. The era with the most amount of slang would be the 1940's. Yes the 1940's. Rappers think they heve the most but they are wrong. Watch the 1940's film "Fire ball" about an english professor and some young people come to visit him with thier slang.  Of course the slang from the 1940's has gone away. Just like in the year 2040 Rap phrases will be gone.