While reading about a British Doctor Doom here, I learned that DC Comics had created their own "Dr.Doom" way back in 1950, many years before Stan and Jack used the nom de crime for their Fab 4 master villain. The DC Dr.Doom was a one-shot Atomic Age character who appeared in Detective Comics a single time, and appeared to die in a final fashion at the story's end.
The story written by Edmond Hamilton, goes that while taking an inventory of their one thousand trophies in the Batcave, Batman and his youthful ward Robin get a call from Commissioner Gordon about a smuggler named Dr.Doom. They arrive to see the villain seemingly drown, but little do they know that he has hidden himself in a mummy case. That case ends up in the Batcave where the sinister Dr.Doom appears with a improvised plot to kill off the Dynamic Duo.
But his scheme falls short and Batman and Robin survive while Dr.Doom himself gets trapped inside the air-tight case and suffocates. The air fully out of his villainy he is apparently never deemed worthy of revival (even by the likes of Steve Englehart) and so remains among Batman's long list of deceased enemies.
And that's why the name "Doctor Doom" was ready and waiting when Stan and Jack needed it for their malevolent mastermind in the full bloom of the Silver Age.