An 1879 Atlantic article described how the movement was taking hold in Germany at the time. “The workman … was told that every man has a right to the necessaries of life,” it reads, and “that while one single person suffers, no one has a right to luxuries.”

In the United States, socialist organizations emerged beginning in the late 19th and early 20th centuries and aligned themselves with the struggle for labor rights. The term socialist was sometimes applied critically to social liberal policies such as the New Deal to characterize them as radically anti-democratic and un-American. Particularly through its association with the Soviet Union and communism, McWhorter observed, the word has taken on a certain “menacing” tenor for Americans, who identify it with foreignness, atheism, lack of patriotism, threats to civil liberty, and a certain glum grayness.

“People have associations with it that are negative,” McWhorter said, “and that’s not going to change.”

In general, McWhorter explained, words tend to take on more pejorative meanings with time. Notorious once simply meant famous, for instance, and obnoxious meant vulnerable; now both are unambiguous insults. The same has happened to socialism. “That sort of thing is natural,” he said. “ And one can scarcely think that you can reverse these basic conceptions that settle in among all of us.”

Sanders’s and Alexandria Ocasio-Cortez’s efforts to specify that they represent democratic socialism, McWhorter said, “doesn’t work,” because the term is still weighed down by socialism’s negative connotations.

On top of that, he noted, neither Sanders nor Ocasio-Cortez nor any other prominent Democrat is really proposing introducing a socialist program in the United States to the degree it exists in Denmark or Norway. So, as in the case of liberalism, the meaning of the term is muddled by its application to differing political ideas and situations.

Read: Trump’s new red scare

All the associations that have been fixed onto these words, McWhorter contended, have made them “so opaque that they impede discussion rather than allowing it.” He pointed out that this defeats the purpose of language itself, which is to communicate an idea in a way that others can understand.

McWhorter argued that progressive is a far better term for the people and ideas described as liberal or democratic socialist today. Unlike liberalism, which communicates only a vague relation to liberty, he said progressivism is “etymologically transparent” in its clear signification of progress, of moving forward. And unlike socialism, the term doesn’t require supporters to clear “cobwebs” of negative historical and tonal associations when they identify with it; though progressive was formerly attached to the Progressive movement that arose in the late 19th century and the “bomb-throwing radicals” of the late 20th, McWhorter said that over the past decade, that baggage seems to have dropped away.

McWhorter contended that adopting a new term was simply a matter of accepting a reality of language: The meanings of all words tend to shift over time. Their uses grow more and more pejorative. Their origins are clouded by the different contexts they move through. Progressivism, he warned, will be no different. He gives it “roughly 20 years”—and then a new term will have to be found once again.