There is a belief that the reason why cops are called so is because in the olden days, police officers wore copper buttons on their uniforms. Copper got shortened to cop which ended up entering the slang dictionary.
This is however not completely true. The word ‘cop’ has always existed as a verb that meant ‘to take or seize’. However, it’s meaning underwent several linguistic shifts and finally settled on ‘to arrest’ or ‘to take into police custody’. As a result, policemen began to be called ‘coppers’ which eventually got shortened to ‘cops’.
The term “coppers” can be traced back tot he early 19th century in new york city when the first police force consisting of an 8 men unarmed patrol unit wore on their shirt an 8 point copper badge to distinguish themselves as officers of the law. as a result the general public started calling them coppers