The goal of any fandom, ultimately, is to connect with other people. “Hey, you like this thing? I like this thing too!” Accordingly, fans frequently like to think of their fandom as broadly inclusive. As long as you like that same thing, that’s all they care about.
In 1959, science fiction fan Dick Eney picked up on the earlier work of Jack Speer (under the name John Bristol) to create Fancyclopedia II, a dictionary of terms used in fandom. As we see online today, fans often create their own words and expressions that might not make immediate sense to those outside a relatively small circle. While Speer tried to capture as many as he could, Eney’s version was substantially expanded and a much more comprehensive attempt at defining the terms of fandom. And on page 56, we find the following entry…
Phrase coined about 1940, applied to Jack Weidenbeck, who roomed with fans and enjoyed their company, but shunned all responsibility in fan doings and institutions. Generally speaking, one who hangs around fans but takes no active part in fan affairs, and may not read fantasy. Fans are, after all, at least theoretically fantasy enthusiasts; fake fans are fandom enthusiasts. They don’t read prozines. (Sometimes they don’t even read fanzines.) They don’t remember vast numbers of insignificant details about fantasy stories and their authors illustrators and publishers. They don’t collect books or proz. Fake fans do not have the haggard look that is the mark of the true fan trying to keep abreast of the latest developments in stfdom. And there are some fans who like to describe themselves as fakefans to symbolize disinterest, but their continued fanac belies them.
It would seem that at least as far back as 1940, members of a fandom were so regularly making arbitrary decisions on what constituted being a “real” fan that they began establishing criteria to make sure guys like Weidenbeck there couldn’t claim to be a fan themselves. The Fancyclopedia has more than a few other terms that illustrate how exclusionary they were trying to be: crud, deadwood, dressed-up mundanes, femme fans, goshwowboyoboy, etc.
In practice, we see that fandoms often adopt an Us versus Them mentality. In many cases, this isn’t surprising given that people gather to form fandoms frequently because they’ve been excluded from other groups. They then become protective of their own group and use “rules” to ensure none of those people who would mock them sneak into the group. It guarantees their fandom is a safe space of sorts where they can practice their hobby with some measure of security.
The specific expressions of exclusion obviously vary from fandom to fandom, and even within a single fandom over time. (I’m pretty sure I’ve never seen “goshwowboyoboy” outside a now historical context.) But the intent remains. And that’s, sadly, one of the reasons why we continue having discussions about “fake geek girls” or what-have-you.