Abbreviation of "Fo sheezy my neezy" which is a bastardization of "Fo shizzle my nizzle," which is a bastardization of "Fa Shoh mah Niggah," which is a bastardization of "For sure my Negro" which is the bastardization of "I concurr with you, my African Brother."
Specified from KungFuJesus Apr 28, 2003 suggestion.
Abbreviation of "Fo sheezy my neezy" which is the bastardization of "Fo shizzle my nizzle," which is the bastardization of "Far show my Niggah," which is the bastardization of "For sure my Negro" which is the bastardization of "I concurr with you, my African Brother."