Quiz: Remember the definition of mal de mer?
"peep show contained in a box," 1680s, so called "in imitation of the foreign way of pronouncing rare show" [Johnson]. "Johnson's statement is prob. correct; the early exhibitors of peep-shows appear to have been usually Savoyards, from whom the form was no doubt adopted" [OED]. Early "peep shows" were more innocent than what usually was meant later by that word.