I think your best friend calls you 'kutjoch', which is a rude (but not uncommon) name you can call a boy who annoys you. It's mostly used by young people. If you translate it literally, it means *a obscene word for a womans genitals*-boy (a girl can be called a kutwijf, which means *a obscene word for a womans genitals*-women). I think the English equivalent of 'kutjoch' is ***hole, or ****head, but the difference is that 'kutjoch' can only be used for boys, not for grown men.