Basically the combination of "Nigga" and "Fag"
It's not necessarily meant to be racist against African Americans or bigoted against Homosexuals. Mainly it's using the definition of "Nigga" that is basically like "Homie" and the definition of "Fag" which insults someone because they're a lame dumbass, not necessarily because they're gay. Just like how "gay" has just become a general term for something "lame".
"ICP FOREVER BITCHZ"
"Man, you're SUCH a niggag."