AIBU to feel hurt by my partner's sibling's comment about our baby?

Jokes are meant to be funny.

I’ve heard people ask this as a way to suggest the name is made up. Maybe she thought you were trying to be rude.

It may not be a typical question but it's well within normal parameters in any English culture that is interested in language and there are a few of us left. It doesn't usually carry the implications you have attributed.
However the ' normal defensive' retort of " it's better than the name you chose so back ' in your box' is very out there whether literally or in sentiment. No one comes at new mothers like that and I feel sad that you think this is normalised.

Your hormones are all over the place and so are hers, try to forget about it, I really don't think it meant anything. You reacted in the right way at the time.

Cross posted with OP.
Apologies 🤭
He couldn't suppress his inner bitch 🙄
Better?

It’s more likely he meant “my baby’s name is better than your baby’s name” rather than my baby is better than your baby.
but either way it was a comment between brothers who are both exhausted new parents. You should not make it about you or get involved or even give it any thought. Even if the four of yoy are close, brothers have their own relationship which might involve in-jokes or spikyness or even genuine competition but it doesn’t need to bleed out to you and sil and the children.

Probably a joke but not very funny.
My youngest has an unusual name, which isn’t English and people have asked where it is from
and the meaning. I have always thought they were just interested and been happy to ask.
If it was a joke then it obviously didn’t go down well, which I am sure they were aware of.
I would forget it for now but if they make any other comments in future just have a word about it

Ignore!

It was the OP's partner's brother who made the comment.

Storm in a teacup, I feel. I hope that in a few years you will be able to tell the BIL and wife how hurt you were at the time, and laugh about it as an overreaction. (Yes, probably because you are hormonal, but also parents are OF COURSE fiercely protective of their baby and programmed to overreact to any perceived insult. Not your fault!)

There’s no way this is a common conversation:

person 1: meet my new baby Charlotte Jane.
person 2: what does that mean?

It means my new baby is called Charlotte Jane. Does Charlotte Jane have some origins / totally unconnected or made up meaning - probably… but it’s just an insulting question.

“Better than Elthelbert Prudence” is a pretty normal defensive response - as in “it’s a better name than you chose, so back in your box”.

What does that mean comes across as a weird and intrusive question where you can’t think of anything nicer to say. And it might be a bit embarrassing to say you don’t know, like the insinuation is you’ve not been diligent enough in naming your child if you don’t know the meaning of the name.

You are being over sensitive to what was obviously a joke. Calm down and enjoy your baby. Cousins aren't automatically best friends anyway, so stop worrying about things that haven't happened yet.
Oh and please don't ever mention their 'gender disappointment' to the parents because that would be such a horrible thing to do.

I think you've misunderstood. In my culture for instance, all our names have meanings so its a standard question to ask anybody. Some brits are aware of this, so when meeting someone from that culture, will ask the meaning of their name or their baby's name. They're not being snippy, its just a nice question to ask because they usually all have nice meanings. Its rather unfortunate OP's sil took offence.

For those saying it was a joke: it didn't sound very much like a joke, and if it was, don't you think OP would know? Would there have been an awkward silence that followed? Please stop gaslighting people into thinking they're overreacting over these kinds of things.

Was it meant to be a joke? Weird and rude as fuck.

If you think you might be feeling hormonal, and this baby is even younger - she could also be feeling a bit oversensitive from hormones.

I've just had to Google the meanings of my kids names because in 16 years of being a parent no one has ever asked me! So interesting lots of people think it's a normal question. I just chose on what sounds nice and who else I knew with those names. I'm glad they didn't ask me as actually the meanings don't suit us at all! Whoops!

It was a weird rude comment from them, but if things are usually ok between you I'd put it down to a misjudged joke, or them feeling awkward for some reason (eg embarrassed they don't know the meaning or taking all your questions to mean you didn't like it).

Well most 'English' names aren't really English and have original meanings in other languages. Sarah is a Hebrew name meaning princess, Katherine a Greek name meaning pure, William a Germanic name meaning strong-willed warrior etc. I don't even know the meaning of my own name- i could Google, but it's the kind of thing I forget very quickly.

But back to the OP, this is the kind of thing my brother would say to me to wind me up. He wouldn't actually mean it to be taken seriously. Insensitive to say to a new mum though.

They made themselves look stupid. I would let it go tbh if you normally get on with them well.

My first response on being told a babies name is to say “what a lovely name”, not “what does it mean”.

Obviously the babies name wasn’t Charlie or Sharon, because you would not have asked that question had it been, but because it was not an English name you assumed it had a meaning.

Imagine if everyone asks “what does it mean” on being introduced to new baby? It would most probably get a bit irksome.

@Alawishus39 what was your first instinctive thought on hearing the babies name?

Was it ‘what a lovely name’? Was it ‘Ooookay!’ or was it “what does it mean”?

I have had a number of ‘oookayy’ moments on first hearing babies names.

I think what they said is very odd and I'd be upset.

If you've got on well previously I'd let it go ultimately and hope it was a one off

I’m going to suggest there is competition/rivalry between the brothers and you got caught in the crossfire. If you can do anything it’s to maintain a really good relationship with the brothers wife and ignore all the nonsense between the brothers. Then you’ll be fine.

Love how everyone is still blaming the sil even though the OP says the remark came from her bil.

@Alawishus39 it sounds like a joke that fell flat. If you can overlook it, that would probably be for the best.

You said to her" ooo ahh umm what does that name mean" which sounds rude to me , youve both got hormones,

I’ve recently had a baby, less than 6 months ago and partners sibling has just had theirs, they are both our first babies.

People assumed because OP said she’s just had her baby and her partners sibling has just had theirs, so it could be assumed that she meant gave birth like she meant for herself.

I don’t think it matters who said it but I’ guess if it was the sibling it would have been easier to call them out on it, so I guess it’s relevant to a point but I don’t think the sex is relevant.