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"Big Bad."

It's a phrase you may have read before, particularly in relation to genre TV shows. Whether you're talking about a superhero show like "Arrow" and "The Flash," or a supernatural show like "The Vampire Diaries" or, er, "Supernatural," they all have an over-arching, season long villain that showrunners -- and characters -- like to call the Big Bad.

But where did the phrase first come from? What's the ultimate origin of "Big Bad?" on TV? Turns out, it can all be traced back to one show: "Buffy the Vampire Slayer." And more specifically, it was first mentioned back in the 1998 episode "Bewitched, Bothered and Bewildered," an hour written by "Buffy" writer and former showrunner Marti Noxon.

Noxon is currently finishing up the first season of her new show "Girlfriends Guide To Divorce" on Bravo, but took the time to recall just where the phrase first came from. Turns out, though, it was a little harder to remember the exact moment of origin... For a very specific reason.

"Honestly, that was one of the episodes that I kind of air balled!" Noxon told MTV News over the phone, laughing, about writing the episode. "There weren’t many that Joss [Whedon] really said, 'uh, you kind of missed the mark,' but that was one I think I was writing over Thanksgiving or Christmas, and the tone was really sort of farcical. So that was one he rewrote a fair amount of. I would say Joss came up with that on his own."

In the second season episode, Buffy (Sarah Michelle Gellar) refers to the season's uber-villain Angel (David Boreanaz) as, "the big bad thing in the dark," a phrase that presaged its first true onscreen use in the season three episode "Gingerbread."

From there, "Big Bad" was off to the races as it were -- though it's an expression Noxon recalled was bandied about the writers room long before the characters themselves started using the phrase on television.

"It became part of our vernacular as much as anything else," Noxon noted. "We absolutely were [using it] without even realizing it. The ways the characters talked became the ways we talked."

That's because, according to Noxon, there was a distinct effort on the part of the writers to create their own slang, something that creator Joss Whedon felt would make the show timeless.

"The more you use a popular slang the more something gets time capsuled," Noxon said, "and when I watch old episodes of 'Buffy' there’s not a lot of sort of '90s talk."

And though it may not have been a conscious effort on their part, the phrase has become timeless... Even if Noxon can't remember the exact moment the term was hatched.

"Was it a line that Joss wrote in my script, was it a line I wrote?" Noxon mused. "It all gets a little fuzzy because we all worked so closely together and traded scripts back and forth... But it’s pretty much a guarantee if it was super sticky, it's from him."