A lyric in a song known as "Dre Day". This was a song created in 1992 by Dr. Dre, Snoop Dogg, and featured a few other rappers. The lyric: "So if you want to keep poppin that shit and get your mother fuckin cranium cracked, step right up!"
This is probably what a lot of people on this site are probably going to end up have happening to them.
This word is used to describe someones balls that have been beaten by either being stepped on, slapped, punch, bit, flicked, kicked or even set on fire which would end in the result of (Cracked balls).