Hi-- Just wanted to point out that that is something that men sometimes do as a way of being affectionate, using the same "guy" bonding things--surnames, nicknames, fist bumps--with women that we do with men. And I get that sometimes that can feel really sweet, or.... just the opposite and really annoying or demeaning. A few years ago I got a girlfriend upset when I responded, very genuinely, to her helping me with something by hugging her and saying "Aww, you my dawg" (immature, I know, but that's the part of me that was touched). She got upset that I "referred to her as a 'dog.'"
OK, I get that--that word can make people feel all different types of ways. Not what she was wanting just then. So I promised not to do that, explained why I did, and apologized in advance if by any chance it should it slip out again in the future. This is a rather long-winded way of saying that the same thing can mean different things to different people and that it is worthwhile to clarify for him how you feel about it. I would take seriously how he responds to your request--that he not minimize it, explain it away. Neither of which I mean to do, by the way, just trying to offer something that might be helpful.