AIO My boyfriend and his best friend won’t stop calling me his ex’s nickname

My (f22) boyfriend (m22) and I have been dating for 10 months. He (Spencer (fake name)) has one really good best friend (Elijah) that he calls, texts, and games with every single day. They both are bilingual and speak Bosnian as well as English, but I noticed they would call me “Aba” in both English and in Bosnian.

When I asked my bf why he called me that, he explained how he used to see this girl called Abby and that was their nickname for her. I will say they never officially dated, but they were romantically involved with each other. He went on to explain how when he and I were first talking with each other, Elijah mentioned how I looked similar to Abby. And from then on they started to call me Aba. My bf says that they use the nickname interchangeably with the word “baby” since “aba” means “baby” in Bosnian, however I’ve found no evidence online indicating that.

When I learned he was essentially calling me his ex’s nickname I was immediately filled with disgust and I asked him to stop calling me that and to discourage Elijah from calling me that as well since I was so uncomfortable with it. After trying to defend himself and Elijah, he eventually agreed to stop.

Fast forward a month or so later I came home early from work and overheard him calling me Aba over his headset. I was immediately met with that same feeling of pure disgust. After I let him know I was home, we had an argument about how he blatantly went against his word to stop, and I tried my best to make him understand how hurt and upset he made me. He told me they had gotten into a habit of calling me Aba before I even brought it up in the first place, and so it’s been difficult to stop saying it, and apparently he told Elijah how uncomfortable I was with it, and Elijah didn’t think it was a big deal and just wouldn’t stop calling me that no matter how hard Spencer tried telling him not to.

I told him I didn’t care and that they both needed to stop calling me that or else I’d leave. Since then, I haven’t heard either of them say the word.

Tonight however, I was playfully looking on Spencer’s phone and I half-swiped his messages on Snapchat with Elijah (I know, I really messed up with that), and I saw that Elijah was still calling me Aba. I’m literally shaking while typing this and feeling everything- nauseous, confusion, betrayal, etc.

I guess I don’t know if it is purely a slang term in Bosnian for “baby” or if I need to bring this up again or potentially break up with my boyfriend.

Am I overreacting with either thought???