Slogans have emerged from American protest movements, successful and otherwise, throughout history. The American Revolution furnished the world with “Give me liberty or give me death” and the still-popular “No taxation without representation.” The equal rights movement in the 1960s used the phrase “59 cents” to point out the income disparities between women and men. The civil rights movement embraced the song “We Shall Overcome” as a slogan. During the Vietnam War, protesters called on politicians to “Bring ’em Home” and “Stop the Draft.” More recently, supporters of Mr. Obama shouted “Yes, we can.”

The idea behind the 99 percent catchphrase has its roots in a decade’s worth of reporting about the income gap between the richest Americans and the rest, and more directly in May in a Vanity Fair column by the liberal economist Joseph E. Stiglitz titled “Of the 1%, by the 1%, for the 1%.” The slogan that resulted in September identified both a target, the “one percent,” and a theoretical constituency, everyone else.

Rhetorically, “it was really clever,” said David S. Meyer, a University of California, Irvine, professor who studies social movements. “Deciding whom to blame is a key task of all politics,” he wrote in his blog about the phrase.