Rebecca Tyrrel: Had Marie Osmond been the seventh child, she could have called herself 007

Who knew that Marie Osmond's given name is Olive? Why in the world did she change it? There are two credible theories. Either little Marie was concerned that, what with her mother being an Olive too, the household was in danger of becoming a grove. Or she intuitively understood that there never had been a showbiz star called Olive, and never would be.

The only Olives ever to become household names are Olive Oyl – the proto-feminist whose first words to future boyfriend Popeye were "Take your hooks offa me or I'll lay ya in a scupper", and hardly a role model for a demure Mormon girl – and Olive (Rudge) from On the Buses, who was never going to be a role model to anybody.

It might have been different had Olive been the seventh Osmond born to the senior Osmonds rather than the eighth. Then at least she could have called herself OO7. But she wasn't. That was Donny and DO7, weirdly, does not have the same ring.

Until the recent challenge of Willard Mitt Romney, Marie was definitely the most famous Mormon ever to go by her middle name. But there are signs that she has always wanted to acknowledge her birth moniker – for when she turned down the offer to play Sandy in Grease it wasn't because the script did not meet her high moral standards as is always claimed, it is because she wanted someone with the closest name to Olive, ie, Olivia (Newton John) to have a go.

And what golden days these are for the Church of the Latter Day Saints. Last year there was Mitt, now The Book of Mormon in the West End. Donny and Marie are invited but a friend piously insists: "It's never going to happen. They take their faith very seriously, and have no interest in seeing it mocked in the name of what some people call entertainment".

Some people called the Donny & Marie show entertainment, and today, at 53, Marie still duets with her elder brother in a Las Vegas variety show. She also passes her time, in the traditional rock-chick fashion, designing Victorian-style dolls, and to celebrate the 50th anniversary of the Osmonds first stirrings as the Von Trapps of Mormonism, she created Olive May, a cute little madam. The limited edition of 5,000 is made not just of china but also in China, and it sold out. Bless her, she paid her dues to the name Olive in the end.