It's actually the other way around - they already had the symbol X and that's why they became USX. New York Times, July 9, 1986, on the founding of USX: https:

It's actually the other way around - they already had the symbol X and that's why they became USX. New York Times, July 9, 1986, on the founding of USX: https://www.nytimes.com/1986/07/09/business/us-steel-new-name-ends-an-era.html https://www.nytimes.com/1986/07/09/business/us-steel-new-nam... "Mr. Roderick explained that for months the company had considered more than 200 new names, ranging from U.S.S.A. and Amcor to Maxus. U.S.X. was selected, he said, because ''it had a continuity from the U.S. part.'' He added that X had been the company's symbol on the New York Stock Exchange since 1924. " There's no obvious connection between X and US Steel - maybe somebody just thought X sounded cool?