I think it's a short story. I probably read it in the 1970s. Somehow an alien finds a wardrobe containing one wire coat hanger that has a paper cover on it with the name of a dry-cleaning business. From this meager evidence, the alien deduces everything about humans and the English language. Other than that, I don't remember anything about the plot.
This is "Cabinet Meeting" (1977) by Michael Bishop. The protagonist of the story is President Henry David Thoreau Montoya y Florit, and the coat hanger is hanging in his "chifforobe," the only article he was able to salvage from the White House and move to the New White House in Forgan, Oklahoma. (Subsequently renamed "New Washington;" things are not going well for the United States.)
The aliens are contacting President Montoya through the chifforobe, and ask him to enter it to meet him, and then explain how they have learned what they have about Earth:
"From the coathanger we have made well-informed projections about the level of your technology, the morphological development of your species, the weight you give to material as opposed to spiritual cognition (and vice versa), and the psychological derangements attendant upon, as well as the meteorological conditions conducive to, the wearing of clothes. The syntax and the vocabulary of your language we deduced from the slogan on the coathanger’s wrapper: 'The Y.T. Blasingame Full Service Laundry and Dry Cleaners of Washington, D.C. We Get You Back on the Street, Looking Neat. Professional Alterations at Inalterably Low Prices.' "
It's an amusing story, and you can read it in the Internet Archive's copy of Asimov's, Summer 1977.