Wayne Rooney's baby Klay and the trend for K-names

Footballer Wayne Rooney and his wife Coleen have called their second son Klay. The name is more usually spelt Clay. It's part of a wider trend that is seeing "c" being substituted with "k".

Think of famous people whose names start with the letter K - when they once would have been a C - and one word springs to mind.

Kardashian.

There's Kourtney Kardashian, Khloe Kardashian and mother Kris.

Sister Kim might not fit the bill, but then she used to be married to a Kris. Now's she dating another K - Kanye West.

The Kardashians aren't the only family who have colonised the letter K.

Former US baseball star Roger Clemens and his wife also adopted it, taking the alphabet association one step further by given their four sons - Koby, Kory, Kacy and Kody - second names beginning with the letter A.

The K calling was to honour Clemens's strikeouts - each known as a "K".

The Rooneys' first son is called Kai. So by adding Klay - which commentators have speculated could have been inspired by Muhammad Ali's birth name Cassius Clay - to the family, they have joined a growing club.

"Substituting a C for a K has been the single favourite trick of creative baby namers over the last decade. Substituting a Y for an I is another favourite," says Laura Wattenberg, author of the Baby Name Wizard.

"And K attracts people who like alliterative kids names, pairs of names. The letter stands out in look and sound, you can't miss it."

There's even a term for this type of creative spelling - "kree8iv" - according to Pamela Redmond Satran, co-owner of Nameberry, who cites the US actor Patrick Wilson, who called his son Kassian, and skateboarder Tony Hawk, who called his daughter Kadence, as other converts.

Boys names such as Kameron, Konnar and Kaylob, and girls names such as Kaydince and Klaira are also on the rise.

"The substitution is part of trend which is seeing parents come up with inventive ways to make their children's names more unusual.

"Personally, I think old vintage names or ethnic names are a better way to make a child's name individual, but people love creative spellings. I think the Kardashians have made it tacky chic," Satran says.

Parenting club Bounty.com's spokeswoman Lisa Penney agrees celebrities have a huge influence on baby name trends.

"After the Rooneys named their first son Kai, it leapt up the charts to the 48th most popular boy's name for us, and it's still ranked 60th.

"We've had over 24 kids called Keegan already this year, and 54 Rios, probably after Rio Ferdinand. And Hugo made it into the top 100 last year, climbing 61 places, which we put down to the popularity of Made in Chelsea," she says.

When it comes to Clay or Klay, Penney says there have been 284 spellings of the name starting with the letter C on the site since 1995, versus 28 starting with the letter K.

But she says she wouldn't be surprised if Klay climbed up the ranks.

And it's not just baby names that are seeing the K effect catch on.

Ian Brookes, consultant editor for Collins Dictionaries, says brands, goods and retail establishments have increasingly been using K instead of C, or Z instead of S, over the last 20 years because people have felt less restrained, or restricted to, traditional forms of spelling.

"K, X and Z in particular can be seen as fun and funky letters, which can be used in unusual circumstances to give punch and effect.

"Kids Korner and Kidz clubs are pretty common nowadays. And people have been buying Rice Krispies and Heinz Beanz for ages," he says.

In fact, Brookes says there is no real need to have the letter C in the alphabet, because the sounds it creates can be replicated by a K or an S.

"Most English words which begin with K are borrowed from German or Japanese, like karate or karaoke. So by using K or Z, it could be that we are suggesting something exotic in some way," he adds.

But linguistics expert Prof Vivian Cook thinks it is quite the contrary.

"In the UK it has been used by businesses mostly at the cheap end of the market."