呕

Left-side mouth radical — pictograph of an open mouth, the small square shape. The indexing radical, doing the obvious semantic work: 呕 is to vomit, to retch (呕吐). The mouth is where the action happens. Same family of mouth-sound-expulsion characters: 吐 to spit, 吼 to roar, 喊 to shout, 咳 to cough.

Right side 区 supplies the sound: qū → ǒu, an attested shift in the qū / ōu / kòu phonetic series. 区 depicts items stored within an enclosure (traditional 區 had three 口 inside — district, sector). Same phonetic family: 欧 Europe, 鸥 seagull, 殴 to beat, 驱 to drive. Recognising 区 unlocks the whole reading set.