Why does he call me a slut, whore, etc??

There is this guy who I'm good friends with and we have been for a pretty long time now. We tease each other and joke about stupid stuff all the time. However, he has this habit of sometimes "jokingly" calling me a whore or a ho or a slut (and trust me, I am the FARTHEST thing from that). We're good friends so I wouldn't think he's saying those things out of spite or to be rude but still why in the world would a guy call his friend that? And please don't say "well you're obviously not friends" because, trust me, we are.
Why does he call me a slut, whore, etc??
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