When Fox News host Megyn Kelly gamely took on Erick Erickson, a contributor to the network, for his provocative statements about gender roles last week, she was puzzled by one word in particular that Erickson had used to describe his ideological opponents. "I don't know what the word is... some sort of liberals, eco-liberals, what did you call them?" "Emo liberals," Erickson clarified.

Erickson's emo epithet is a clipped form of emotional, which may seem like an obvious bit of shorthand. After all, English speakers have used demo for demonstration since 1936, and promo for promotion or promotional since 1955, according to the Oxford English Dictionary. But there's a complex cultural backstory behind the emo shortening.

Emo emerged in a couple of extremely disparate American contexts. One was among the staff of Cosmopolitan under the editorship of Helen Gurley Brown beginning in the mid-'60s.  Brown, who had a lingo all her own, referred to magazine articles on emotional subjects as "major emo." After Brown's death last year, Ralph Gardner recalled in his Wall Street Journal column that when he wrote for Cosmo in the '80s and '90s, the editors compiled binders of story ideas labeled "emo" and "non-emo."

It would be hard to imagine a social milieu more different from Cosmo's offices than the Washington, D.C. hardcore punk scene of the mid-'80s, but emo bubbled up there as well. The January 1986 issue of the skateboarder magazine Thrasher told its readers that there was a new style of hardcore that "goes by the name of Emo-Core or Emotional Core." Bands fitting this description "are taking the severe intensity of an emotional projection, and adding it totally into their respective live sets," the magazine explained. "Crowds are said to be left in tears from the intensity."

The bands singled out by Thrasher immediately rejected the emo label. Ian MacKaye, then playing with the band Embrace, bitterly complained about the magazine's write-up to the crowd at one show: "Emo-core? Emotional hardcore? As if hardcore wasn't emotional to begin with. Anyway, it's caca."

The name stuck nonetheless, with emo-core soon replaced by the simpler emo. When emo returned as a musical genre in the late '90s, it had moved on from its D.C. hardcore roots to a more accessible style, though the lyrics of the new emo bands were as emotionally sensitive as ever. The popular success of the emo genre brought with it a rapid mainstreaming of the term emo itself, often applied to stereotypical aspects of fans of the music, such as their hair, fashion, and dour demeanor.

As the word spread, the meaning of emo became more diffuse and difficult to pin down, with more than a thousand conflicting user-generated definitions contributed to Urban Dictionary. As Andy Greenwald wrote in his 2003 book on the emo scene, Nothing Feels Good, "emo seems solely to mean different things to different people—like pig latin or books by Thomas Pynchon, confusion is one of its hallmark traits."

That confusion didn't stop emo from moving beyond the world of music to other realms, such as media and politics. In January 2005, the New York Observer referred to CNN's Anderson Cooper as an "emo-anchor," and the appellation fit him even better later that year when he passionately covered the aftermath of Hurricane Katrina. Broadcasting & Cable magazine observed that Katrina "served to usher in a new breed of emo-journalism," with Cooper as its chief practitioner.

Since emo has so often been used pejoratively, it's no surprise that conservative pundits would add the term to their arsenal of liberal putdowns, an update of sorts to the old standby, bleeding-heart. As Geoffrey Nunberg details in his book Talking Right, bleeding-heart was popularized by the columnist Westbrook Pegler in the New Deal era and persisted as "a durable phrase that reduces all altruism to girlish sentimentality." Emo now takes its place on conservative blogs like Erickson's RedState, where the word can imply that those on the political left are not simply emotional but emotionally unstable. Twenty-first century political rhetoric can spring from some unlikely sources.

Click here to read more articles from Word Routes.

Ben Zimmer is language columnist for The Wall Street Journal and former language columnist for The Boston Globe and The New York Times Magazine. He has worked as editor for American dictionaries at Oxford University Press and as a consultant to the Oxford English Dictionary. In addition to his regular "Word Routes" column here, he contributes to the group weblog Language Log. He is also the chair of the New Words Committee of the American Dialect Society. Click here to read more articles by Ben Zimmer.