Mid 17th century; earliest use found in John Milton (1608–1674), poet and polemicist. From classical Latin aethereus, aetherius + -ous; compare -eous and -ious.
Definition of ethereous in US English:
ethereous
adjectiveɪˈθɪərɪəs
rare
Ethereal.
Origin
Mid 17th century; earliest use found in John Milton (1608–1674), poet and polemicist. From classical Latin aethereus, aetherius + -ous; compare -eous and -ious.