欧

Right side 欠 — pictograph of a person with mouth open, exhaling. The indexing radical here. Original meaning of 欧 was the act of opening the mouth wide (to vomit, to sing out). The radical groups 欧 with 歌 sing, 歇 rest, 欲 desire — all open-mouth actions.

Left side 区 supplies the sound: qū drifted to ōu with vowel shift but kept the same Old Chinese onset family. Originally 欧 meant 'to vomit / to sing' (an open-mouth exhalation); the modern senses 'Europe' and the surname Ōu are phonetic loans. Same phonetic gives 鸥 ōu (gull), 殴 ōu (beat), 沤 òu (soak).