What is the origin of empyrean?

Empyrean “the highest heaven” ultimately derives via Late Latin from Ancient Greek empýrios “fiery,” from pŷr “fire,” which is the source of words such as pyre, pyrite, and pyro- and is distantly related to English fire. The Ancient Greeks believed that the world around them comprised five elements—fire, water, air, earth, and ether—and although ether was considered a distinct airlike element found in the upper atmosphere, there was some overlap with fire; ether (Ancient Greek aithḗr) was related to the verb aíthein “to burn” and was considered together with fire to constitute the heavens and emit light and heat. Empyrean was first recorded in English in the early 1600s.