An admission of jealousy. "I'm so jealous". An adaptation of the phrase "miso horny", which is a mutation of the phrase "me so horny", which is a poorly translated version of the phrase "I'm so horny". But with jealousy instead of horn.

Miso jelly could also conceivably be a type of food, which facilitates humourous use of the phrase as a pun.

When you eat dirt for the first time and leave your family to build a shack in the woods