I had this with my DH 26 years ago now when I was pg with our middle child. (Obvs we didn't realize he would be our middle child at the time i was pg)
So we had a girl, then a boy and, at an earlyish scan, the sonographer said she thought this 3rd one was a boy.
At that point, i started to bond with him as a boy and DH voiced no objection to my preferred name.
Unbeknown to me, he really was hoping the sonographer had been wrong and he wasn't comitting to it being a boy until it was properly confirmed later in the pg.
Of course - at a later scan, boy.
And, same as you, DH had no name - he just didn't like my choice. But, in my head, i'd already got to know my boy with his name.
It became quite a source of stress in the pg. Finally - about a day before the birth DH announces his choice of name - Darren!!!!
Sorry to anyone out there that does have sons called Darren but no way was that happening. Even the midwives sympathised with me.
So, our son was nameless for a day or two and then DH gave in.
Our son turned out to be a very slow developer and was eventually diagnosed with autism and learning difficulties. He LOVES his name though. It's a name often seen on street names, pubs, monuments etc and every time he sees it he points it out, proudly saying
"There i am, again!"
DH now admits it is the perfect name for him. Stick to your guns, OP!