An unlicensed beer shop, a kiddlywink was permitted to sell beer or cider but not spirits like traditional taverns and inns. So shopkeepers would keep contraband brandy in a kettle under the counter. The knowing clientele, often smugglers and other disreputable types, would then wink at the kettle when they needed a top up. Farm labourers could visit a kiddlywink to receive beer instead of their wages.
For more fun Cornish slang and words, pop over to the BBC.