Well, the issue really isn't whether Ansan is the name you want to use, it's that he's stuck on something and you don't like it anymore.
I hear ya, we go through the same thing. DH is pulling up names he rejected for DD#1 and is now stuck on one of them that I like but am not sold on. Meanwhile, the name that I really like for this DD#2, which we never considered for DD#1, he intentionally mispronounces (and it's not hard to pronounce) and does the passive aggressive crap to try to get me off of it. However, it's my turn to name the child (first name,) since he picked DD#1's name, and he gets a middle name. But he's not doing that, saying he can't pick one or even consider one until the FN is settled. I get that, but he won't just say, go with the one you like, he hopes he'll wear me down.
All I can suggest is tell him that those older names are out, and keep working on new names. Hopefully, if you tell him enough that the names Milo & Elliot are out, he'll open his mind to other options. GL!