Why are police referred to as cops?

Around the year 1700, the slang verb cop entered English usage, meaning "to get a hold of, catch, capture." By 1844, cop showed up in print, and soon thereafter the -ersuffix was added, and a policeman became a copper, one who cops or catches and arrests criminals. Copper first appeared in print in 1846, the use of cop as a short form copper occurred in 1859.