I don't know for sure, but I suspect it has something to do with oral sex.

""-izzle" is a suffix used to produce a "secret" language or cant, similar to Pig Latin, in African American and hip hop slang. It is sometimes called "Snoop speak" because it was popularized by Snoop Dogg, but it was used much earlier by Frankie Smith in his 1981 hit single "The Double Dutch Bus". Carnies (carnival workers) have used "iz" in precisely the same fashion for centuries. A dialect emerged from the practice of adding "ee-uz" after each consonant, and was dubbed "Ciazarn" (from the dialectized form of "carny")." "Shizzle is a rap slang word for "sure", coined by E-40 and popularized by rap star Snoop Dogg. It has been adopted by several rappers and reggae deejays and is commonly used as: fo' shizzle as in, "for sure", often paired with "my nizzle" as in, "my nigga". This pairing became popular after Snoop Dogg used it in his song, "What's My Name (Part 2)" on his Album Tha Last Meal. At the beginning of the song, Snoop talks over the beat: Izzle kizzle, fo' schizzle My nizzle, what you sizzle? Fo' schizzle bizzle, ha ha (Lyrics) Snoop Dogg himself probably did not expect the phrase "Fo' schizzle my nizzle" to gain such popularity. First, the phrase is broken by a long pause on the track itself, suggesting that Snoop himself considered "Izzle kizzle, fo' schizzle" to be one phrase ("It's okay, for sure") and "My nizzle, what you sizzle?" to be another ("My nigga, what you say?"). Snoop's laughter at the end of the blurb further suggests that the whole intro was just meant to be a joke, albeit one that caught on quite broadly. The song Double Dutch Bus, written by Frankie Smith originally spawned the use of 'izzle' as a suffix for words. While used in its purest form and true meaning as listed above, izzle as a suffix was rarely used, with exceptions occurring in a song now and then. But as the pop and rap scene grew increasingly successful, the phrase became quite popular. Those who heard the phrase, not understanding its meaning, often misinterpreted it, and further spread it without fully understanding it. This has led to the use of Shizzle to mean "shit" to replace any noun in popular speech, much like "shizznit", as in "my shizzle's hella fizzle, yo." Such terms can be used in slightly more polite company, or to get past censors on TV or radio. "Shizzle my Nizzle" has also become a popular phrase to express surprise in New Zealand, popularised by Glen Browne who is also the author of the wildly popular Diggy Dr Brzay's word of the Dzay." Source and further information: http://en.wikipedia.org/wiki/-izzle Snoop Dogg - Snoop Dogg (prod. by Timbaland) http://www.youtube.com/watch?v=m5G7e7SO-EQ