anger
恚 centers on a deep, festering anger or resentment, often held in the heart.
恚 combines 圭 (a doubled earth shape, possibly suggesting piled-up or accumulated) with 心 (heart), indicating anger that builds up in the heart. The exact historical development is uncertain, but the component structure is consistent with a phono-semantic compound where 圭 may have contributed a sound element.
Picture two mounds of earth (圭) pressing down on a heart (心), like piled-up grievances that create a simmering anger.
For イ, imagine the anger is so intense it makes you say 'Ee!' (イ) through gritted teeth, as the piled-up earth crushes your heart.