Comes from the word "whack"
"whackshack" Is a term used to define someone unconventional almost to an insane degree. The kind of person that will jump off a 3 storey building into a bush to impress people can be refferred to as such.
Also can mean the house or hang out area for people who are whack
Person- Did you see jonathon run cross that busy street last night?
Other person- Yeah, he's a total whackshack.
Come on boys, let's just leave them to go back to their whackshack