Yours, Etc.: Origins and Uses of 8 Sign-Offs
1510s, "of the highest regions of the atmosphere," from ether + -al (1); extended sense of "light, airy" is from 1590s. Meaning "spiritlike, immaterial" is from 1640s. Related: Ethereally.
ethereal e·the·re·al (ĭ-thēr'ē-əl)adj.
Characterized by lightness and insubstantiality; intangible.
Of, relating to, or containing ether.