There’s also a story (or maybe just a tall tale) that at one time Manhattan Project engineers used “copper” as a code word for one of the radioactive materials they were working with. At some point they needed actual copper, which was then code-named “honest-to-goodness copper.”
The battleship Pennsylvania, newly refloated after Pearl Habor, got silver bus-bars in its electrical system for the same reason. Wonder if they recovered them before it was sacrificed as a target ship at Bikini.