Peep show
A peep show or peepshow is an exhibition of pictures or objects viewed through a small hole or magnifying glass. This may or may not be a sex show, although the latter kind has eventually become the most common usage of the term since the advent of cinema and television, which destroyed various kinds of entertainment provided by wandering showmen.
History
Peep shows, also known as peep box or raree show ("rarity show") trace back to ancient times (15th century in Europe, by Leon Battista Alberti) and are known in various cultures. It could be a wooden box with a hole or several holes. It contained a set of pictures which the show-man can set into a viewing position by pulling the corresponding string. The boxes could be decorated inside to resemble a theatrical scene. The show was accompanied by "talk show" that explained what is seen or what expected to be seen.
Possible shows were exotic views and animals, scenes of classical drama or masques, court ceremonies, surprise transformations, e.g., of an angel into a devil, and of course, lewd pictures.
Raree shows were precursors of toy theatres, with movable scenes and paper figurines, popular in the 19th century.
Sex shows
By an analogy, the term "peep show" is applied to a piecewise presentation of pornographic films using a coin-operated gadget, which shuts the view after a short time period, requiring more coins to be deposited for continuation.
"What the Butler Saw" machines are an early example of peep show gadgets.