How do I explain to my (20F) boyfriend (27M) that my family tradition is really important to me?

TLDR: My bf thinks naming our future kid my middle name is setting them up to fail in life, how do I explain how important this is for me?

Me and my bf have been dating for almost a year now and have known each other for over two. I know there is a big age gap between us so please no judgement on that, if you knew us in real life you would think we were the same age.

Before we became official we sat down and talked about some traditions we have and what both our future paths looked like, I told him then that a family tradition of mine was to name the first girl after the mothers middle name. He was cool with it at first but after finding out what my middle name was he was against the idea, we choose then that we would come back to the topic after we had been dating for a while and I was cool with that.

A bit of background on my middle name, I got to choose it. I sat down with my mum about 10 years ago and we discussed names, that's when she brought up that my actual name wasn't the name she wanted to give me. She was in love with the other name but my dad hated it, so they went with my mum's middle name as none of the other girls in her family were planning on having kids. I instantly feel in love with the name and told her I wanted it to be my middle name as I would love to name my future kid that name.

The topic came up the other day (we have tried to talk about it in the past but he would get annoyed with me about it so I would drop it), we were talking about how if we had a daughter he wanted to give her a middle name that honored his late grandma. I was more than happy for this as she was a big part of his life. I brought up the subject on my middle name again and once again got shot down, no way was he going to name his kid that it was "setting her up to fail". He can't get past the fact that it is a brand of car, I had no clue that that brand even existed until this year and most people I talk to have never even heard of it.

He came up with an ultimatum that we would look into names together and choose one we both liked so that we could name our kid that way and I would just have a double middle name. I don't really like this idea as I truly have my heart set on this name and just wish he could see where I'm coming from.

How do I explain to him that this is really important to me? I feel like I've tried everything

EDIT: I realise I didn't make this clear but I'm not the first to do it, my mum's side has done it for generations. But I'm the first to choose my middle name as my parents couldn't decide on one.