So that “I will not rejoice” quote that everyone reposted yesterday wasn’t from Martin Luther King, it turns out. Instead, it looks like it originated with a young woman in Pennsylvania who had no intention of hoaxing anyone. She just posted her own thoughts on Bin Laden’s death to Facebook, and the rest is internet history.

If your Twitter feed and Facebook page look anything like mine, yesterday various versions of the quote were all over both:

“I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy. Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness: only light can do that. Hate cannot drive out hate: only love can do that.” –Martin Luther King, Jr.

The problem is, though, that King never said that. Or rather, he said the last three sentences, but not the first.

The bulk of the quote comes from a 1957 Christmas sermon of King’s, in the following context: “Let us move now from the practical how to the theoretical why: Why should we love our enemies? The first reason is fairly obvious. Returning hate for hate multiplies hate…” But the beginning part, the “I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy” part — the part that seems to apply most directly to the death of Bin Laden — appears nowhere in King’s writings, nor does it appear anywhere online before yesterday.

So where did it come from? The Atlantic’s Megan McArdle, who was the first to pick up on the quote’s falsity, tried and failed to track it down. About an hour ago, Drew Grant at Salon claimed that magician/objectivist/prankster Penn Jillette was the first one to post it to Twitter, saying he suspected that “Penn just made it up in order to see how many people would blindly follow along and quote it as fact, without ever checking up on the sources.” (Penn quoted only the first sentence — the part that’s not King’s at all.)

Penn denies making anything up, though, and has in fact gone into full self-flagellation mode on Twitter. And by the time Grant posted, someone else had come forward with what looks to me like a more plausible explanation:

Late last night Jessica Dovey, a recent college grad from Pennsylvania, sent Penn a tweet saying that the quote was hers, posting a screenshot from her Facebook page explaining how the confusion started. Here’s what went down, she says.

Early yesterday afternoon she posted a status update to Facebook that read like this:

I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy. “Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness: only light can do that. Hate cannot drive out hate: only love can do that.” MLK jr

Note the location of the first quote mark. Dovey wrote the first sentence as an expression of her own views, appending the King quote as a further explanation.

I haven’t seen any evidence to back this claim up, and it’s possible it’s a hoax of its own — I just tweeted Dovey to ask her for more info — but my first reaction is that this seems completely plausible. The original quote, as McArdle pointed out, never quite rang true. In addition to the weird specificity, there’s an abruptness to the transition that clangs a little against the mind. But when you move the quote mark, that abruptness disappears, and the whole thing flows.

More generally, it’s my experience that a lot of these false facts start out just this way — not with a conscious attempt to propagate a lie, but with something that gets misquoted, misunderstood, or misrepresented entirely by accident. We’ve seen this happen with stories as different as the beer pong herpes scare of 2009 and the claim that only 4.7% of American blacks voted in the 2010 elections.

It’s hard to get a hoax right when you’re doing it on purpose, but it’s weirdly easy to get one going by accident.