Well, first of all, we must wave away fiction (as we sadly often have to do...) when it comes to history. The idea of women fainting at the sight of terrible things or even their mention is not as old as history. We have no suggestions (to my knowledge) of medieval French women, ancient Egypt women or Mayan Mesoamerican women fainting at the sight of blood, spiders or hearing that the priest has seduced a local teenager.

Indeed, this occurrence took place mainly in the Victorian area and was a combination of several different things. For it is true, women did feint at regular and irregular occasions during these years but the reasons aren't simply as vague as "the female mind".

Let us start with corsets.

In the nineteenth century (and other time periods) the corset was extremely popular among women who could afford choking and being immobile to look pretty. As such, this was primarily something for bourgeois women and upwards, as female farmers, factory-workers, nurses and what not would find it impossible to work in the corsets of the 19:th century.

Worn around the chest (and thus the lungs and the intestines) corsets were often made out of wool or leather, tightly woven and supported to so called "boning", which were vertically placed "ribs" of a sort made out of whale-bone, ivory or in the cheaper kind, wood. The purpose of the corset has varied, sometimes it's produce a curvier look, sometimes it's to suppress said curvier look. During the Victorian era it was definitely the former.

Girls did not start wearing corsets as they became women (which might seem logical, because that's when you start getting curves) but rather girls started wearing them at a -very- young age. As in, pre-teen age. Take a look at this nifty commercial from the time-period.

So, what happens if you wear something that presses on your chest in general and your ribs in particular for a great part of your life, including growing up when you form said rib-cage? Well, they get permanently displaced, that's what happens. As a result, lungs get compressed, intestines get shoved around, hearts struggle to function properly as the body struggles to function properly.

Eating disorders followed, as there simply wasn't enough room to eat anything but the mere minimal.

---

With that said, it's highly likely that a lot of the swooning and fainting was put on display. It was simply a fad, it was lady-like, it was proper and it was considered nice. A lady that did not feint and swoon was no lady at all. Finer houses all included a so called 'feint-room', which was a pretty neatly set up room in some distant, silent corner of the big house. It had a feinting couch, soothing light, probably a bit to drink and so on and so forth. It was a social retreat where you could bring one or two friends with you while excusing yourself for a moment.

Additionally, -some- of the wealthier houses could afford a midwife or a doctor to help treat 'hysteria' which was a very common diagnosis at the time. In 1859, physician George Taylor for instance made the claim that 25% of all women suffered from hysteria. Hysteria had several treatments, including high pressure cold showers and other shock-therapies... But the most commonly accepted one was that it stemmed from sexual desire. As such, midwives or doctors could be working around the clock in these "fainting-rooms", offering pelvic massages to women who needed to take a break. As such, there was a pretty decent incentive to suddenly feel a need to feint and withdraw to hang out with your two best friends, have a cup of wine and get some... massage. There are reports of doctors filing complaints of pained wrists and fingers due to having to work with as many patients as they did (once again to underline here, this really was NOT a problem for poor people, who could not afford fainting rooms or doctors to staff them).

The sexual treatment of hysteria lead up to the development and invention of the vibrator who at first required medical personnel to handle but sooner rather than later (to the doctor's great lament!) became hand-held and easy to use on their own. The fad eventually grew out of fashion and the corsets of today are quite comfortable and women seldom feel the need to feint when watching the SAW movies. A more commonly accepted behavior is to gasp or simply avert your eyes when you encounter something shocking.

Sources: Tystnadens historia (History of Silence) - Peter Englund (2005)

EDIT: Before we go bananas on corsets, I'd like to underline that 21:th century corsets are fine, even comfortable at times.