(n.) someone who works or socializes at night, and sleeps during the day
A coenobite is a member of an enclosed monastic or religious community. It’s derived from two Greek roots, coenos, meaning ‘common’, and a derivative of bios, meaning ‘life’.
Based on that older and fairly established term, in the first century AD the Roman philosopher Seneca invented his own name for quite the opposite: lychnobite.
Here, the second part of the word remains the same, but the first has been replaced with lychnos, a Greek word for a lamp.
From Seneca’s Epistles in AD 65 we can jump forwards a few centuries to 1727, when the English lexicographer Nathan Bailey included the word lychnobite in his Universal Etymological English Dictionary. He defined it (somewhat dramatically) as a “night walker”—but other scholars of Seneca’s work, and later lexicographers since, have called it simply a ‘living by lamplight’, or in the words of the Oxford English Dictionary, a “fast-liver”, who “turns night into day.”
In other words, if you spend more time working, socializing or partying after dark than during the day, then you’re a lychnobite.