A common British nickname for police officers is 'coppers'. This nickname derives from the verb 'to arrest' or 'to grab', in essence, 'someone who captures'. Often, 'copper' is shortened to just 'cop'. The nickname was first used around 1704 according to Oxford English Dictionary (OED).

There are several incorrect stories about how 'coppers' got their nickname. One suggests the name refers to a policeman's copper buttons or copper badge. Another proposes that 'cop' is an acronym for either 'constable on patrol', 'constabulary of police', or 'chief of police'.

Many other nicknames have emerged over the years for police officers, including 'City Kitties', 'Old Bill', 'Boys in Blue', 'the Fuzz', 'Plod', 'Rozzers', and 'Bobby'. The latter came from a nickname for Sir Robert Peel (1788-1850; 'Bobby' is a nickname for 'Robert'), the founder of the Metropolitan Police in the UK.

A police officer is a member of a police force with the authorisation to arrest criminals, prevent crime, and keep public order. Some police officers have specialist roles, such as detective, traffic officer or police dog handler. In Britain, only experienced police officers carry guns, whereas in other countries it is more common for all or most officers to be armed with a weapon.

More Info: en.wikipedia.org