It would have been better for the supervisor, to say, I appreciate your bringing your concerns to me, but as of right now, I haven't been informed, of any concerns about you.

Yes, 'fo-shizzle', is slang. It's modern terminology, these days, used to be ghetto slang, but hey! It has crossed generational and cultural lines. I don't fully appreciate your co-workers reaction, but threatening to tell on you, isn't 'cool'. All your co-worker needed to say, was, could you please not use that term around me. And if you respected that, great. And then, if you did it, again, then your co-worker would have the 'right' to complain.

I get where you were just trying to protect yourself. Hang in there, there's growing pains in any job, no matter how long, anyone has been there!