Etymology
1898-12, Charles F. Brush, edited by J. Am. Chem. Soc., A new gas., volume 20, page 909:
[...] it seems really probable that it not only extends far beyond the atmosphere, but fills all celestial space at a very small pressure. In recognition of this probability, I have provisionally named it aetherion or etherion, meaning “high in the heavens.”
From Ancient Greek αἰθέριος (aithérios), from αἰθήρ (aithḗr, “upper heaven”).