The word stems from the French jalousie, formed from jaloux (jealous), and further from Low Latin zelosus (full of zeal), in turn from the Greek word ζήλος (zēlos), sometimes “jealousy”, but more often in a positive sense “emulation, ardour, zeal”  (with a root connoting “to boil, ferment“; or “yeast”).
The color green is often associated with jealousy and envy, from which the expressions “green with envy”, and “green-eyed monster” are derived.
The term Green-Eyed Monster, originally coined by Shakespeare, represents the envy that we feel. The jealousy that consumes us. The comparison that leads us to sin. It’s a feeling that leads us to unhealthy habits.
Everyone struggles with envy. Our culture is obsessed with comparison with the “Joneses.” We are discontented people.
In our culture, of what are most people jealous?