City slicker is an idiomatic expression

Idiom

Idiom is an expression, word, or phrase that has a figurative meaning that is comprehended in regard to a common use of that expression that is separate from the literal meaning or definition of the words of which it is made...

 for someone accustomed to a city or urban lifestyle and unsuited to life in the country. The term was typically used as a term of derision by rural Americans who regarded them with amusement. It may mean "fop

Fop

Fop became a pejorative term for a foolish man over-concerned with his appearance and clothes in 17th century England. Some of the very many similar alternative terms are: "coxcomb", fribble, "popinjay" , fashion-monger, and "ninny"...

", or it may be a derogatory term for a man in a city-type business suit and businessman-type personal attitude in areas where such attitude to life is unwelcome.

City slicker was derisively given to these Easterners for their assumption that their "book-learnin'

Education

Education in its broadest, general sense is the means through which the aims and habits of a group of people lives on from one generation to the next. Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts...

 " gave them superior intelligence. Nineteenth- and twentieth-century Westerners, particularly cowboys, used the Easterners' perceived snobbish attitudes as justification for playing tricks—sometimes violent tricks—on them.

City slickers appeared often as deceitful characters in U.S. comic strip

Comic strip

A comic strip is a sequence of drawings arranged in interrelated panels to display brief humor or form a narrative, often serialized, with text in balloons and captions....

s and movie

Film

A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

s before the middle of the 20th century, but usually to be "outsmarted" by the native wisdom and common sense of the locals or to somehow otherwise get their just deserts in the end.

The archetypal city slicker is depicted as a spoiled selfish lazy rich person who considers people living on farms to be poor and ignorant. They are depicted as being unaccustomed to hard labour and as a result, tire very easily and complain when working.

The term is still used in rural areas today.