顎
あご · ago · JLPT N1 · noun
chin
頁 head + 咢 open mouth = jaw. Sounds like ago: say ah and your chin drops
The kanji 顎 combines 頁, a head radical, with 咢, which carries the sense of an open mouth. Together they point to the lower face. It is read ago, like 'a go' as the jaw swings open.