The story
Green was long tied to feeling sick, perhaps from the pale, greenish look of someone unwell, or from unripe green fruit that gives a stomachache. Shakespeare ran with it: he wrote of “green-eyed jealousy” in The Merchant of Venice and called jealousy “the green-eyed monster” in Othello. “Green with envy” is a later spin on the same idea, from the 1800s.