Chocs and cigs and ripping and topping

I blogged about Books v. Cigarettes, a collection of essays by George Orwell, a few weeks ago - but there's one more passage I'd like to share with you. Here he's writing about the years immediately preceding the First World War:

It was the age when crazy millionaires in curly top-hats and lavender waistcoats gave champagne parties in rococo house-boats on the Thames, the age of diabolo and hobble skirts, the age of the 'knut' in his grey bowler and cut-away coat, the age of The Merry Widow, Saki's novels, Peter Pan and Where the Rainbow Ends, the age when people talked about chocs and cigs and ripping and topping and heavenly, when they went for divvy week-ends at Brighton and had scrumptious teas at the Troc.

I just love how Orwell captures the spirit of the period primarily through its vocabulary.

And does anyone know what a 'knut' is in this context?

Bone and horn idle

I'm currently reading Books v. Cigarettes, a collection of essays by George Orwell. In the final essay, 'Such, Such Were the Joys', Orwell writes about his schooldays and recalls his old headmaster saying:

Go on, you little slacker! Go on, you idle, worthless little boy! The whole trouble with you is that you're bone and horn idle. You eat too much, that's why.

'Bone idle' I know, but I've never come across 'bone and horn idle' before. Googling it brings up only three results, one of which is 'Such, Such Were the Joys'!

However one of the other Google results suggests that 'bone and horn' (usually shortened to 'bone') is rhyming slang for 'born'.

That's plausible, but I have one reservation: 'bone' and 'born' are only one vowel sound apart (at least in my non-rhotic accent), so using one to stand in for the other seems a little... pointless.

In all the other examples of rhyming slang that I've come across, the original word and the replacement word are not at all similar-sounding. It must make for a more effective cryptolect, if nothing else.

What do you think?