Frustrated

My husband and I had talked before we were even married that he wants to name his first boy after his grandpa, which I was totally fine with since I knew how close he was with his grandpa. Fast forward a few years, I’m now pregnant and every girl name I give him, he instantly says no to, doesn’t even give it a second thought, and it’s so frustrating because I don’t particularly like his grandfathers name but I’m willing to name our baby that if it’s a boy because I know how happy that would make him. I’ve brought this up to him but nothing changes, and as soon as he thinks of a girls name it’s like it’s instantly the best name ever and he thinks it should be set in stone. Ugh I’m just so annoyed with this