Coconut

Recently Xolani Gwala called one of his colleague a coconut. I have been trying to find out what conclusions can be drawn in order for one to say someone is a coconut, the reason being, when I was growing up I was fond of imitating English speaking presenters or actors and I went as far as adopting their accent. I did not attend a model c school nor go to a white university. Is an accent one of the thing that determine if you are a coconut or not? I was once called a coconut and it never bordered me. So if someone out there knows the answer please enlighten me.