late 14c., from L. æther "the upper pure, bright air," from Gk. aither "upper air," from aithein "to burn, shine," from I.E. base *aidh- "to burn" (cf. Skt. inddhe "burst into flames," O.Ir. aed "fire," L. aedes, see edify
). In ancient cosmology, the element that filled
all space beyond the sphere of the moon, constituting the substance of the stars and planets. Conceived of as a purer form of fire or air, or as a fifth element. From 17c.-19c., it was the scientific word for an assumed "frame of reference" for forces in the universe, perhaps without material properties. The concept was shaken by the Michelson-Morley experiment (1887) and discarded after the Theory of Relativity won acceptance, but before it went it gave rise to the colloquial use of ether for "the radio" (1899). The name also was bestowed 1757 on a volatile chemical compound for its lightness and lack of color (its anesthetic properties weren't fully established until 1842).