Oh and there are several in house terms for police officers amongst each other, to recognise each other in public without giving the game away, usually in the form of specific phrases.
But I'm not going to let on here
The most common one used by cops every day in the UK hasn't even been used on any police progs on TV yet. But it's used all the time.
Probably because it's such a common everyday word, that everyone of you uses everyday that no one has detected that it also means copper/police force between police officers when in dangerous/embarassing/incriminating out of uniform circumstances