In 2005, a scholar at the Smithsonian Institution's National Museum of Natural History, Ives Goddard, published a paper asserting that redskin had benign origins. Goddard traced the word to phrases used by Native Americans to describe differences in skin color with colonists, which were translated by French-speaking arrivals in the 1760s to peau-rouge and then into English. In the early 1800s, redskin was used by white people and, in translation, Native Americans alike. "I turn to all, red skins and white skins, and challenge an accusation against me," Black Thunder, chief of the Meskwaki, said at a War of 1812 treaty conference, according to a translation published in a national magazine, Niles Weekly Register.
But as violence against American Indians became government policy, redskin as used in newspapers and literature assumed a derogatory sense, framed in stories about savage Indians and righteous white Americans. In the first edition of Merriam's Collegiate dictionary in 1898, redskin was labeled "often contemptuous." In the unabridged editions of 1909 and 1934, the label disappeared. What happened? In the first half of the 20th century, Native Americans, increasingly perceived as a dying race instead of as foes on the frontier, faded from mainstream consciousness except as mythologized caricatures in pop culture: Wild West shows; cigar store Indians; The Lone Ranger; John Ford movies like Drums Along the Mohawk and Stagecoach; advertisements using words like wampum and heap-big; and sports mascots, like Chief Noc-a-Homa of MLB's Atlanta Braves. (Dictionary.com labels the second noun sense of brave, "a warrior, especially among North American Indian tribes," as sometimes offensive.)
The aforementioned NFL team was founded in 1932 in Boston, where it played for a few years before moving to the capital, and originally was named the Braves. To avoid confusion with the city's baseball team of the same name, owner George Preston Marshall renamed the team in 1933. He chose the replacement in order to keep the team's red-and-white logo, a profile of a Native American in a headdress. Marshall was an avowed segregationist who went on to football infamy: He was the last NFL owner to sign African American players, in 1962, and then only after President John F. Kennedy threatened to evict the team from its brand-new home, District of Columbia Stadium (later renamed for the slain Robert F. Kennedy), which sat on on federal land.
To the white purveyors of popular culture, Native American stereotyping appeared harmless. Which means that the uses of redskin in the sources read by Merriam-Webster editors were seen as harmless, too. The word was used as a synonym for "American Indian" for so long and with such deeply embedded casualness that it might have been unrecognizable as offensive to the editors who dispassionately collected usage samples and drafted definitions from them. That was white culture failing to recognize how the people being defined—Native Americans—viewed the word doing the defining—redskin. The nickname of a sports team wouldn't have raised an eyebrow.