I think I'd be tempted to just say, "wow, how rude."
Wow. I'm not sure why I'm surprised at how rude people can be, but I am. If someone is being rude to me, I tell them, "You're being rude." They usually don't have a response to that.
Moron: "Indie? Huh. That's a weird little hipster name."
Mom: "My, my, you're a rude little person, aren't you?"
Toss your hair and walk away. They'll go home and tell their friends and family about the weirdo they met that was so rude to them. But you'll go home knowing you stuck up for yourself, and your choices. Hopefully your children observed you and learn that it's totally okay to let people know when they're being RUDE; and, further, that it is not okay to talk to other people like that.
You can't please all of the people all of the time.
Since your daughter is actually named Florence Imogen, nn Indie, perhaps this person felt more within their rights to discuss the name Indie itself (as it bears no actual relation whatsoever to your daughter's given name). Your other two children's names are fairly ornate and upper-crust sounding, which again might invite comparisons by someone who thought you were closer than you are.
Personally I think if you're snippy in return you come out looking worse than simply saying "well, it's done now, isn't it?" or "we love it, it's meaningful to us because of X, Y and Z."
My sons name is Levin. It's not for everyone. That is okay, b.c we love it, it is very meaningful to us, and it fits him perfectly. I am not holding out for universal popularity. My name was unusual while I was growing up (less so now) and I have gotten many rude comments on it. I just always figured if it wasn't my name, it would be something else.
Mostly, no one says anything negative about it. I really don't think most people are just waiting around for an opportunity to be rude, you know? But when people do unkind comments about it, or wrinkle their noses, I feel embarrassed for them. Seriously, what kind of awful things could be going on for a person who feels compelled to insult a baby's name? So I just pretend that they said something appropriate.
Stranger: "What's his name?"
Stranger: "Really? What a terrible name!"
Me: "Thank you. We love it, too."
This generally just confuses people and they give up.
Ha ha ha tarynkay! Love it! Victory through confusion ;-)
I actually love the nn Indie! So cute. I probably would have just raised my eyebrows at them until they looked away :-)