The *term* originated earlier, as a form of self-mocking on the left, but the *modern concept* originates with the expropriation of the term by the right, starting with a series of articles in The Atlantic and other outlets in the 80’s.

Edit: the Wikipedia page, https://en.wikipedia.org/wiki/Political_correctness, has extensive historical coverage, noting that, in the 70s, “ the term was often used as self-critical satire” — that was my first exposure, when a feminist theorist lover referred to herself as a “political lesbian” but she liked men too much to be entirely “politically correct”. I learned a lot of cultural inside info when I inquired about that phrase.

The article connects the rise of the modern pejorative sense to Allan Bloom’s “The Closing of the American Mind” and a series of articles in the New York Times … no mention or citation of articles in The Atlantic that I distinctly remember reading at the time … but perhaps my memory is playing tricks on me, as I myself have not been able to locate such articles.