envy, admire, praise, covet
羡 centers on longing for something desirable that belongs to another: envy, coveting, or admiring with a wish to possess. The praise sense is a natural extension of looking up to something with desire.
羡 is a variant form of 羨, which combines 羊 (sheep) with 㳄 (drool), suggesting desire or longing, perhaps from the image of a sheep salivating over something desirable. The modern form replaces the upper 氵 with a simplified shape.
The top looks like a sheep 羊 with a little extra, and the bottom is 次 (next). Imagine a sheep eyeing the next pasture with drool, full of envy and admiration.
For イ, picture an eager person saying 'Ee!' (イ) with wide eyes, coveting what someone else has.