Epicurean “fond of or adapted to luxury or indulgence in sensual pleasures” derives via Middle English from Latin Epicūrēus “of Epicurus.” Epicurus (in the original Ancient Greek, Epíkouros) was a philosopher of Athenian  origin (340-270 B.C.E.) who flourished in the late 4th and early 3rd centuries BC, and his school of thought.  Epicurus taught that pleasure is the highest good and that virtue is the greatest pleasure.  In other words, you're encouraged to eat, drink, and be merry, for tomorrow you many die. 

The Oxford English Dictionary (OED) cites evidence of "epicurean" being used in English around 1400, or sometime in the Middle English period (1150-1500). 

Was Epicurus an epicurean? The answer I was taught many moons ago was a very clear no as we struggled through Lucretius’ De Rerum Naturae. History has not been kind to the subtleties of his philosophy and his Stoic enemies won the reputational battle.

Just the facts:

EPICUREAN Definition & Meaning - Merriam-Webster