So, in a rap tune of recent vintage, our narrator (after surviving an almost fatal car accident) says "the doctors told me I had blood clots, but I'm not Jamaican, man." I checked with my brother, an afficionado of both rap and reggae to see what the heck was meant by this line. He says (and please ignore the lack of caps - he is of Gen Y), "blood clot, or bumba (sp) clot is like a derogatory statment about someone in jamaica. not really sure how it started but basically anything +clot is an insult."

I'd love to know the origin and/or specific meaning of the phrase. Can anyone here claret up for me?