Ethereum, the blockchain technology, takes its name from a fictional magical alloy from the Magic: The Gathering card game.
When creator Vitalik Buterin put together a white paper proposing his open-source blockchain, he chose its name while searching a list of fictional elements.
"I was browsing a list of elements from science fiction on Wikipedia when I came across the name,” he said “I suppose it was the fact that [it] sounded nice and it had the word ‘ether,’ referring to the hypothetical invisible medium that permeates the universe and allows light to travel."
The entry he came across was Etherium, "is a magical Aether-infused alloy found on Esper, one of the five shards of the plane of Alara."
Sources: The Prophets of Cryptocurrency - New Yorker, October 2018 | List of fictional elements