If we believe the miscellaneous crowdsourcers of Urban Dictionary it comes to us by way of Beyoncé's coinage "bootylicious", which makes it pretty obvious that it derives from "delicious".

I'm amused by this part:

Parents and middle-aged talk show hosts often use this to parody the ghetto culture, much as they latched onto the suffix "izzle".

I do believe the Urban Dictionary has just called me a clueless white talk-show host! Oh well, if the shoe fits... ;)