Several people on here claim this has been "shortened" to
"fo' sheazy my neazy"
In what way is that supposed to be shorter?

"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"

David Letterman said it best: I don't know what the fizzuck I'm talking about.

Meaning:
1. affirmative; For sure, ma nigga

not necessarily in any racial context.
From a branch of urban (American) slang which adds 'izz' or varients of (ie izzle/izzo) to words to create a more rhyme like 'melody' to sentences.

Originated in medival England in the 17th century, this phrase has changed in meaning completely, from the orignal shorthand denotation of "Alas! An advasary has come upon us! To the catupults!" to the modern definition of "Please grease up my penis."

THE REAL DEFINITION!!!

Snoop Dogg did NOT originate the colliquialism of adding the suffix' -izzle, -eezy, -iggedy and so forth to common everyday phrases. If you actually know your hip-hop history, this type of language originated from "Double Dutch Bus" by the Gap Band. Download it and listen. Frequent examples of such rhetoric are sprinkled across the track.

However, to the credit of Snoop Dee-Oh-Double-Gee, he took something retarded and made it sound FULLY SHICK M8!

For shure, my african american friend.