ethereal

If you're burning to know the history of "ethereal," you're in the right spirit to fully understand that word's etymology. The ancient Greeks believed that the Earth was composed of earth, air, fire, and water, but that the heavens and its denizens were made of a purer, less tangible substance known as either "ether" or "quintessence." Ether was often described as an invisible light or fire, and its name derives from the Greek aithein, a verb meaning "to ignite" or "to blaze." When "ethereal," the adjective kin of "ether," debuted in English in the 1500s, it referred specifically to regions beyond the Earth, but it gradually came to refer to anything heavenly or airy.