Coded language, by definition, conveys much saying very little. And so those words allegedly uttered in McKinney, Tex., before a confrontation between police and black teens — “Go back to your Section 8 home” — evoked a particular and vivid set of assumptions.

The words were offensive because of what we think they meant in the charged context earlier this month in which police were called on black teens using a private community pool in a mostly white neighborhood. The teen who recounted what happened described those words as a "racial slur." We can imagine they meant that these children came from poor families, that the government helped their mothers pay the rent, that their quality as people was reflected in the quality of their housing.

In a broad sense, this is an American tradition: conflating where people live with who they are. “We’ve been doing that as a society for a really, really long time,” says Lawrence Vale, an MIT professor who has written extensively about public housing. “And it’s been racialized for a lot of that history.”

This is the history of how public housing in the United States — originally conceived as enviable housing for working whites — has become a prism through which some Americans see poor blacks. It's a history that explains how some of the most visible public projects in big cities became, over decades, almost exclusively black, how the residents living there came to be among the country's most deeply impoverished. Today, households receiving government housing assistance — from traditional public housing to the private-market vouchers it inspired — live on average incomes of less than $13,000 a year.

This is a history that also helps explain how the outdated name of a bureaucratic-sounding federal program, Section 8, became a racially coded put-down. ...