以太 is a sound loan from English "ether": 以 and 太 are there only for their sound. Relativity did away with the ether in physics, but the name lives on in 以太网 (Ethernet), 以太坊 (Ethereum) and its coin 以太币, which crypto talk shortens to 以太.
mistakes
The chemical ether, the old anaesthetic, is a different word: 乙醚.