Why would a guy call a girl a when she's not?

Like with this guy I know named "E". One friend of mine rides his bus and my little sister has his homeroom and they both told me E has said some pretty nasty things about me... Including I'm a . Honestly it kind of made me mad. Because I am not, and E knows that! The furthest I've gone with a guy was a hug, I don't hit on every guy I know, and a lot of people have told me that I am one of the nicest girls they know. I just don't get him. Any ideas why he would say this? Because he acted all freakin nice to me before like we have been friends forever. And when I ask him, he would be all "what are you talking about no I never said that" but I highly doubt that my sister and friend would make it all up.