Berk

'You berk' is an insult you may hear in the UK. It means 'stupid person', 'maker of errors'. It is not felt to be very offensive, although in its original form it was. It is rhyming slang. The 'surface phrase' is 'Berkshire (or Berkeley) Hunt. A similar feature of pronunciation, with the spelling '-er-' representing the sound 'AH^r' can be seen in clerk, the proper noun Hervey and the military rank of 'sergeant'.