ethereal

The word 'ethereal' originates from the Greek noun 'aithēr', which referred to the upper, pure air breathed by the gods, as opposed to the lower, dense air ('aēr') breathed by mortals. This concept was adopted into Latin as 'aether', and later into English as 'ether', initially describing a substance believed to fill the celestial regions. The adjective suffix '-eal', derived from Latin '-alis', was appended to form 'ethereal', literally meaning "pertaining to the upper air or ether." Over time, the scientific sense evolved to denote the volatile chemical compound 'ether', while the primary modern meaning abstracted the ancient idea of the celestial realm into a quality of extreme delicacy, lightness, and otherworldly beauty.

Structure: ether (upper air) + eal (adjective suffix) ether (from Greek 'aithēr', meaning upper air, pure air, sky); eal (from Latin '-alis', an adjective-forming suffix, via Old French '-el').