A friend of mine in my youth was a butcher. He told me that 'back slang' was a way that they could communicate to each other in the shop without upsetting the customers. For as we know the customer is always right? They could loudly refer to a troublesome or fussy customer as a 'tnuc' without causing them to take their custom elsewhere. I think regular shoppers there must have thought that this word was a term of endearment for valued customers?

It must have rubbed off on me as in this equally silly thread What Is it with the World, as I had already used it for the name of an imaginary off-world instrument called the Traf. There is I believe a silent but deadly version of this wind instrument.