A combination of the word "shit" and "nizzle" (slang for business) to form it's compound fusion, Shiznizzle; used to describe anything which has affectively impressive qualities.
Friend of Laid Guy: Yo dude, how was the sex last night with that 10 babe?
Shiznizgit meaning very cool and established taken from from the word shizniz but the added git at the end means that you recongnise wih the person you`re saying it to
Hey Tom you little shiznizgit you just spilt coffe all over my new top!!