From your reference to PIE and your spelling of pedophilia, I assume you're in the UK? Unfortunately I don't know much about this issue in that context - but I can give you a pretty good answer for the US.

First, how do we define the concept of Pedophilia?

Pedophilia is a very modern term, and a very modern concept, which refers not to the act of having sex with children, but rather to a psychological disorder which causes an adult to experience attraction primarily or exclusively to children. This is something quite specific, and it's important to clear this up right away. It's a crummy source but I think this quote from Ray Blanchard puts it quite succinctly: "Child molesters are defined by their acts; pedophiles are defined by their desires."

Where does the term come from?

The first person to use it clinically was a german psychiatrist named Richard Krafft-Ebing, in his work Psychopatia Sexualis (1886), which was a kind of early DSM-like diagnostic catalog of sexual/psychological disorders. It's not until the mid-twentieth century, though, that pedophilia really became a commonly-used term, and it's not until the 1970s and 1980s that it became the subject of as much popular fascination and fear as it is today.

So, what, children were never abused before that?

Not quite - to say that "pedophilia" didn't really exist prior to the 20th Century isn't to say that there weren't adults out there who preyed on children sexually prior to that - rather, it's to say that the people who committed these crimes weren't seen as suffering from a specific psychological disorder, or thought to be defined by their attraction to children. Rather, their actions were understood to be the product of a more generalized sense of moral corruptness and deviancy. Popularly, people like this would have been seen as committing a particularly sick or evil act - but they wouldn't have been regarded as "pedophiles" or "child molesters."

Why wasn't the concept developed earlier?

Well, a few reasons: First: "pedophilia" as we know it requires a theory of explaining criminal or deviant behavior as a matter of psychology, rather than of morality or simple depravity - this is something that had started to develop well before the 20th Century, but it really only becomes the dominant way of framing and explaining a wide array of crimes and other harmful behaviors during the 30s, 40s, and 50s. Second: the development of the notion of "Pedophilia" required a view of children and childhood as sexually innocent; it depends on the notion that children who have sex with adults are corrupted, harmed, or traumatized by the experience. This is something that had long been in development (it starts with the development of concepts of childhood innocence in the 1600s), but it's not until well into the twentieth century that it starts to get universalized (ie, applied to all children) and that gender roles (and legal views of rape/sexual assault) change to the point that victims don't face accusations of having led their molesters/rapists on, or somehow invited the assault. Third: People just didn't talk about this stuff prior to the mid-twentieth century.

Huh? How could people have ignored/been unaware of the sexual abuse of children?

Well, they didn't ignore it - there were lots of individual examples of the sexual abuse of children - many (though by no means all) of which were successfully prosecuted. These cases just weren't covered in the news, and they were talked about only in hushed tones.

More generally, the possibility that there were people lurking out there who might abduct and sexually abuse children - which is how most people picture "pedophiles" today, despite the fact that the vast majority of offenders are family members or acquaintances of the victims - was not something that was popularly understood or acknowledged before WWII. As Paula Fass has noted in her book Kidnapped, before WWII most cases of missing or abducted children were understood to be ransom-related. If you look at famous early kidnapping cases like Charley Ross (kidnapped 1874, never found) and the Lindbergh Baby (kidnapped 1932, found murdered), there's rarely any mention of the possibility of sexual abuse. Media coverage of Leopold and Loeb's killing of Bobby Franks (1924) carried a hint of sexual impropriety to it, because Loeb was later painted as a sexual pervert in the press - but there was no suggestion that they'd sexually assaulted Franks, and as far as can be established, they do not appear to have done so.

I don't have Fass' book in front of me right now so I can't give you an extended quote, but as she says here , "The sexual abuse of child kidnap victims had always lurked as a possibility... but Americans had usually understood this possibility as a danger that was secondary to the ransom that motivated these crimes in the first place."

So when did Pedophilia get recognized and become a public concern?

It wasn't until the 50s that fear of sexual exploitation started to supplant fear of abduction for ransom in the popular imagination, and it actually wasn't until the 70s and 80s that child molesters and pedophiles became something that parents constantly feared. After decades of being used only in narrow academic and professional contexts, the term "pedophile" really only became something that the general public would be aware of after 1968, when there was a sudden spike in references to it in newspaper and magazine articles. Most of these were in turn inspired by new scientific studies of both pedophilia as a psychological disorder and the prevalence of child molestation & abduction. In the years that followed, there were several high-profile cases involving the abduction of young boys - Etan Patz and Adam Walsh being among the most famous - which won far greater and wider media coverage than any child abduction/sexual abuse cases had to date. These cases and the media hooplah over them were what drove the idea of the sexual abduction and exploitation of children to become most American parents' #1 fear. Cases like the McMartin Preschool Trial demonstrate just how much those fears had taken over parents' imaginations by the early 80s.

Why then?

That's a hard question to answer, but the most likely explanation is that the cultural changes of the 60s (the sexual revolution, a sudden rise in crime and fear of crime, the growing sensationalization of news coverage, the new right's assertion that "family values" and families themselves were increasingly under siege) made it possible to talk about the subject. It was no longer taboo to report on sexual abuse when it occurred, and the news media quickly discovered that a fearful American public had a tremendous fear of their children being sexually exploited - and a sort of morbid fascination with the idea of child molestation and pedophilia itself. Once the door was opened to being able to talk about and report on the subject, fear took over and there was this tremendous sense of paranoia about it that started to develop.

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