Etymology

Disputed. Three schools of thought exist:

• From "This will eat your heart out.", suggesting that the recipient of the taunt will have their heart, the core of their being, eaten out with desire, bitterness, or pain.
• From the 16th century "to eat one's own heart" (to suffer in silence from anguish or grief), possibly from the Bible "to eat one's own flesh" (to be lazy) The phrase "to eat one's heart out" appears as a formulaic phrase in the Iliad, meaning to experience extreme grief. (For instance, Iliad.24.128, many other locations.)
• When used as the taunt "Eat your heart out, [someone]!" a suggestion that the recipient of the taunt "eat up" as much as they like. Figuratively more akin to "experience me besting you."