Define Meanie Weenie Meaning

Person A: Hey Pat, you're a mw.
Pat: Mw?
Person A: Meanie Weenie duh, wow get with it.
Pat: Oh right right right. Of course. I agree.

Nice person 1: Ew, have you talked to Josh today?
Nice person 2: Yes, *eye roll* I very much dislike that that ultra meanie weenie