"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 american brother"
Archaic phrase used by African American slaves since the 17th century. A corruption of 'For shine his hall, my knees ill' it was used as a greeting by slaves who had to polish the floors of colonial mansions. Later became an unrelated greeting.
'Missie, missie - yo massah done made me polish dat whole corridor, an it done made my knees hurt terrible - fo' shizzle ma nizzle, an no mistake!' from 'Gone With The Wind' by Margaret Mitchell.
Can i pea on a fire hydrant?
Fo Shizzle My Nizzle... make it fizzle
Affirmitive response.
For sure.
Becky: Are we going to the pub tonight?
Edward: fo shizzle my nizzle