There are many theories for the origin of the term ‘cop’, meaning policeman. Most refer to the copper badge (or buttons) worn by early New York policemen, whereas others cite the acronym for "constable on patrol." Neither is true nor is the colloquialism due to the copper toe tips worn on the boots of some early policemen in the US (Rossi, 2000). The slang verb, ‘cop’, meaning "to get a hold of, catch, capture,” is first seen circa 1704. Most authorities trace it to the French caper and before that to the Latin capere, to seize,or take. Other English words derived from capere include capture. An alternative theory is that to cop comes from the Dutch kapen, meaning to take or to steal. Sir Robert Peel advocated the creation of the Metropolitan Police Force in 1828. By 1844, cop was user in print, and the suffix ‘er’ was added in 1846, to describe one who apprehends i.e., a copper. Cop the noun, was a shorter form of copper. The term flapper to describe a young emancipated girl was common in the 1920s. Typically a flapper wore bright red lipstick with hair bobbed, and hemlines rose as Victorian corsetry was discarded. Smoking of cigarettes and consuming of alcohol became a way of life and flappers were contemporary with the Jazz Age. By 1926 the flappers became so popular that they become a universal symbol and young women. The origin of the term flapper is unclear but may come from Victorian sporting slang for a young wild-duck or partridge flapping their wings while learning to fly. Other suggested sources include: "flap," a young woman of loose character, used in 17th century slang for a prostitute; or late 19th century Northern English slang for a teenage girl too old to be a child and too young to be considered an adult. In Victorian society a 'flapper', would be a young lady not yet been permitted to wear long frocks and the wearing their hair 'up.'" The word appeared in print in the United Kingdom as early as 1903, and by 1920 it clearly meant any young woman of a pleasure-seeking disposition. Flappers' behavior was considered outlandish at the time and redefined women's roles. The image of flappers were young women who went by night to jazz clubs where they danced provocatively, smoked cigarettes through long holders, and dated freely and indiscriminately. Petting became common and Petting Parties, where petting ("making out" or foreplay) was the main attraction, became popular. In the US they openly drank alcohol, a defiant act during Prohibition. According to Rossi (2000) flappers wore unbuckled overshoes so when they walked the buckles flapped loudly.
Rossi WA 2000 The complete footwear dictionary (2nd ed) Kreiger Publishing: Florida