Lucy Cavendish: Sienna picked my little girl's perfect name

Now there'll be armies of little Ottolines

Mummy power: Where Sienna Miller leads, others will follow (Getty Images)

I was happily helping my five-year-old daughter read a book when the phone rang. It was my best friend, shrieking: "Sienna Miller's called her daughter Ottoline!".

"Ottoline?", I said.

My daughter looked up, eyes wide, "Ottoline? That's my name."

Yes. It is true. My daughter is called Ottoline, and even though I found out later that Miller has actually named her daughter Marlowe Ottoline, the damage is done. A celebrity has stolen my daughter's name. I can see it all now – armies of little Ottolines, hoards of newborn baby girls named in deference to tiny Ottoline Sturridge (her father is the actor Tom Sturridge). No one's going to be interested in Marlowe; it's a boy's name (as in Raymond Chandler's private eye, Philip Marlowe), or a town (Marlow, near where I live). But Ottoline is pretty, lovely, easy to shorten – to Tilly, Lina, Ottie. And now? It'll be Ava, Scarlett and India all over again – beautiful names in themselves but these days I meet hundreds of them.

But it's the celeb factor, too. I never considered Apple or Bluebell appropriate for my children. I wasn't interested in Beauregard or Moon Unit. I just wanted names that were slightly original but not irritating.

In fact, it took me, and my partner, my entire pregnancy to come up with a girl's name. We had loads of boy's names on the tips of our tongues. My first son was called Raymond after my grandfather – and Ray Davies and Chandler. "But I never liked my father," my mother wailed when I announced the name of my newborn. This was news to me. It was then that I realised names had meaning, not just as in Lucy means "born in daylight", or Philip means "lover of horses". They have significance, resonance. Names state something about you before anyone has barely even turned to make a judgement about what you look like.

For the three boys, we went for old men/gangster names Leonard (after Leonards Cohen and Woolf) and then Jeremiah (actually after Jerry Leadbetter from The Good Life). Their three names could be Ray, Lennie, Jerry. They'll either be creatives or holding up banks.

But when it came to finding a name for a girl, we were both utterly dumbfounded. I wanted Athena, the goddess of wisdom. My partner vetoed it. He wanted Georgia. I vetoed that. We then went through all sorts of family names; Ann, Susan, Pamela, Juliet. My mother's middle name, Violet, was the choice for a while. I then went totally off-piste and demanded Emerald, Crystal, Honeysuckle, Sapphire. All of these, quite rightly, got chucked out.

In the end, a friend told me she was reading Miranda Seymour's book about Lady Ottoline Morrell. "A fascinating woman," she said.

It turned out that Ottoline Morrell lived at Garsington, not far away. She had a long affair with Bertrand Russell, and my friend now lives in the house he once inhabited. Ottoline was bisexual, a liberal and a bohemian, hanging out with Aldous Huxley, T S Eliot, D H Lawrence, Dora Carrington and Augustus John. Her full maiden name was Ottoline Violet Anne Cavendish-Bentinck.

Was it even important that no one knew how to say her name? We had Otto-line. Otto-leen. The very posh say Otto-lin. No, none of that really matters. My daughter's name was decided – a little bit different, not too different, certainly unique.

Then Sienna Miller blew it all. I know what's going to happen. The less aware will ask me, in years to come, if I named my child after Sienna Miller's daughter, despite the age gap. Or people will scratch their heads and say: "Didn't Sienna Miller call her child Ottoline?"

We thought the name was a little bit unusual, but hopefully not poncey – and now... my daughter is damned for ever!