Not to paint with too broad a brush, but it's probably fair to say that many of us watch tightrope walkers and feel pretty much undiluted fear. But that's a modern audience, bombarded with any kind of scintillating entertainment we want on-demand. It was a little different in the early days of circus, when the sight of a lady wearing trousers could rouse a serious blush.
Think about it — high-wire-walking ladies were going to give everyone an eyeful if they were wearing skirts. The leg-baring doublet and hose women wire walkers wore allowed men to gawk at women's bodies in a way that certainly wasn't socially appropriate for the time [source: Victoria and Albert Museum]. One 1699 review even describes how a wire walker's dexterity might translate well in the bedroom [source: Speaight]. Apparently, watching a wire-walker proved to be a very chaste way to get one's jollies.
But let's peel our eyes from the lady dancing on the rope to learn a little more about the weird origins of the word circus.