Soviet cosmonauts and recovery teams used code words for emergencies to delay their becoming public knowledge before they could come up with the right spin. In one case the code for an emergency mission abort was "Lightning." The cosmonaut, who frankly had too much on his mind to fret over code words, reported seeing a thunderstorm from space, and had to frantically retract the misunderstanding.
Better, they used a "One level better than reality" code, with "Excellent" meaning "Nominal," "Nominal" meaning "Uh-oh," and "Uh-Oh" meaning "Farewell, Motherland!" When the crew of Soyuz 11 died during re-entry, the recovery team broadcast that the cosmonauts were "sick." Nobody could figure out what that meant, or perhaps more likely, everyone knew but nobody wanted to know, and I don't blame them.
As far as I know, the Americans never used code words in any of their in-flight emergencies. It's "Houston, we had a problem," not "The cow moos twice."