"fo shizzle ma nizzle" is a bastardization of "fo' sheezy mah neezy" which is a bastardization of "for sure mah nigga" which is a bastdardization of "I concur with you whole heartedly my African americanbrother"
A bastardised version of "Fo' sho' nigga", which is a bastardised version of "for sure my nigga", which is a bastardized version of "I completely concur my african-americanbrother"