I don't think they'd name a first daughter
Victoria, given that it's looking very likely their firstborn will be the future monarch (it's been agreed, but it's not yet law, so we can't say that for certain yet).
Queen Victoria defined a whole period of history - the Victorian era - a period where there was much change in British society.
I think that's an awful lot for another (potential)
Queen Victoria to live up to.
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Diana as a first name will also be out for two reasons.
Firstly, it's not a traditional royal name, and given that the
Queen will have to give her stamp of approval, it won't pass that.
Secondly, and more importantly, I don't think
William would
want to name a daughter
Princess Diana. I'm sure he realizes, that if he and
Catherine named a daughter this, she would grow up in the shadow of his mother and forever be compared to her. Much better for their potential daughter to grow up away from that.
They'll use it as a middle name, of course they will, but I'd be shocked if they used it as a first name.
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I think
Charlotte is out, as
William's uncle
Earl Spencer (
Diana's brother) became a father for the seventh time in
July 2012, and his daughter was named
Charlotte. Even though it's not the royal side of his family, I don't think they'll duplicate a name used by a family so recently, especially given the fact there'll only be about a year between them.
I don't think
Caroline will feature either, I don't find it regal enough,
Queen Caroline doesn't really evoke majesty to me. (Apologies to anyone called
Caroline).
I think
Matilda is too "trendy" in the
UK right now. I know it's an old royal name, but that was a while ago.
They won't use
Philippa, because even if it's in honor of
Philip, people will assume it's in honor of
Catherine's sister. Traditionally, the family of the "non
Royal" aren't honored in names, for example
William and
Harry don't have
Diana's father's name in their names at all. That surprised me when I first learned of that.
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As for what names I think will be contenders:
*
Mary - it might be simple and sweet, but
Queen Mary just sounds so right.
*
Elizabeth - it honors the
Queen, the late
Queen Mother,
Catherine (her MN) and her mom (also her mn).
*
Margaret - the
Queen's sister, I could see them honoring her.
Queen Margaret sounds very regal.
*
Josephine - I know this was used by another European royal family recently, but it's never really been a British royal name (from what I can tell), but if they're looking to bring in something new but which still sounds royal, this is the name.
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I think
James is out for the boys, it's the
Earl and Countess of Wessex's young son's name, and he is
William's cousin.
I would love for them to use
Arthur, but I don't think they would if their firstborn is a son, because I think
King Arthur is too ingrained in legend.
I think they might use
Albert for a boy, although
Prince Albert is the name given to the piercing of a particular male part of the anatomy (*ahem*), which could count against it.
I actually think
David and
Peter might stand outside chances, both
King David and
King Peter sound very regal.
What I would really love though, is for them to be brave/bold, and revive one of the so-called "unlucky" names, namely
John or
Richard. They were
hundreds of years ago, it's time to bring them back into the royal fold.