From the moment everyone first heard it in Guardians of The Galaxy, the name Thanos has been synonymous with being the ultimate threat in the cosmos. The name, according to the character's creators, comes from the Greek god, Thanatos, who is the God of Death in Greek mythology. This is very fitting considering the Mad Titan's actions and motivations.
But what most people don't realize is this is not the designation he was given at birth. That is correct, Thanos is not the madman behind the Decimation's real name.
This game-changing revelation happened in 2017's Thanos #14 where the twisted warlord spoke with a version of himself that is much older. The conversation revealed that his mother gave him the name Dione before she went utterly crazy because the Mad Titan was too ugly to handle as a newborn.
Like Thanatos, the name Dione does have mythological origins as being the mother of the Roman god known as Venus and is generally associated with sea and water. While most people can agree that Dione is a great name, however, Thanos feels right when talking about someone who gets off on abusing his children and intergalactic mass murder.