"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?
New York Times, July 9, 1986, on the founding of USX: 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?