When I go to London- about once every 20 years on average- one thing I miss is Cockney rhyming slang. It was more than a local underworld cant to fool cops and children; it had its own history; always changing. "Putting your dooks up" in a fist fight, for example. A "Duke (or Duchess) of Teck" was a cheque; "Duke of York" meant to talk, to walk (later ball [of chalk]), or a fork. With the counterpart "Duke of Fife" for knife. But things got confused; the latter could also be 'wife'. Ambiguous and sexually inappropriate, it soon changed to "Duchess of Fife". Thence, by 1880, shortened to "Dutch" (my old dutch). That in turn became "old Dutch china", and "China".(Which was dear!).Helped - since a man's wife was his 'mate', by china for pal or mate (china plate). So "Duke of Fife" was now exclusively knife. Often used not of table-knives, but transferred more to the hands that held them in the street. The fingers of which were suggestive of knives (Dukes/dooks/ Fifes/ bunch of fives, i.e. 5 fingers) or forks (Yorks/ dooks again).To 'put up the dooks' was to engage in a fight; to grease the dooks meant to accept a bribe. An etymology as involved as this lies behind hundreds more rhyming slang words, origins now almost lost. John Barton