Steve Chen, one of the founders of YouTube, named his cat “Pajamas” and the first video played on the website featured his kitty playing with a string.

I like this story for several reasons. First, I find it reassuring that an internet phenomenon built on people uploading home videos should kick off, not with some Jackass-like macho mindlessness, but a domestic pet engaged in innocent play. Secondly, the pet does not have some strange Goth or techie moniker such as Warlock or Gnarly, but a name that is thoroughly appropriate for a small, cute furball.

For me, PJs are garments that are irrevocably associated with memories of childhood - of being tucked up in bed by Mum, and getting up on Christmas morning before the grown-ups to raid the tree. In popular culture, they are reminiscent of Andy Pandy.

So far, so Enid Blyton. But then comes this quote from Playboy's Hugh Hefner: “The pyjamas came early on. I was working a lot at night ... increasingly at the mansion in Chicago, and there wasn't a lot of point getting dressed. Eventually people were disappointed if I was wearing a suit. I've got about 200 pairs, silk pyjamas in 20 colours, and velvet or satin smoking jackets, all custom-made.”

The quote, from an interview in the American men's magazine Details, suggests that PJs may instead be worn by the seducer as a kind of “badge of office”. Add to this the image of the artist Julian Schnabel, who wears his pyjamas out of the house with a jacket or overcoat, his hair unkempt - the very picture of Bohemianism - and we are a long way from Disney duvet covers and bedtime stories.

Indeed, earlier this year fashion designers pushed the idea of jammies as daywear. Prada had silk florals, Miu Miu had chinoiserie styles, Etro cotton Paisley style trousers and Junya Watanabe shirts. In many ways, these designers were going back to the garments' origins. The original pyjamas were loose, lightweight drawstring trousers worn in South and West Asia. The word comes from the Persian “payjama”, meaning “leg garment”.

British colonialists in South Asia in the 18th and 19th centuries took up the idea of pyjamas as sleepwear and imported the style. By the early 20th century they had replaced nightshirts as the norm for bedtime attire in Britain.

Which, frankly, is where they belong. You'll find nice, pure cotton pairs at M&S, and Gap has great plaid pyjama pants, but curiously no tops (I expect you are supposed to wear the ubiquitous T-shirt, though this would never do for Hefner). The Rolls-Royce of pyjamas, though, comes from Derek Rose of Savile Row. So, as the nights lengthen, why not treat yourself to a pair of PJs? Whether you're more Casanova or Airfix modelmaker, they'll suit you either way.

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