ether [LME] This comes via Latin from Greek aithēr ‘upper air’, from the base of aithein ‘burn, shine’. Originally it meant a substance believed to occupy space beyond the sphere of the moon. It was then used, from the late 16th century, as a name for the rarefied substance formerly believed to permeate all space, a sense behind ethereal [E16th]. The use of a volatile liquid as an anaesthetic is found from the mid 18th century. Ethernet, a blend of ether and network dates from the 1970s.