The rap slang “808” has a very interesting origin because of its dual meaning. The older meaning for 808 references the Roland TR-808 Rhythm Composer, a famous electronic music instrument that created most of the distinct synthetic hip-hop sound of the 80s. You might hear it being used like this:
“Grandpa has a legit 808 from the 80s. He was a record producer during that time.
“This party is 808. You better settle down or the cops will come.”
The second meaning is still somewhat popular but the first is seldom used in many conversations, even in rap circles.