The story
Blend of for sure + -izzle (rhyming ending). Popularized by rap artist Snoop Dogg; see -izzle for details. Fo shizzle is a direct derivative of Fa Sheezy popularized by E-40. They both share the same meaning and are used interchangeably. Both words first appeared on media in 1996 on Bay Area Rapper E-40’s “Rapper’s Ball”.
Etymology from Wiktionary, CC BY-SA 4.0.