Left side
曷 supplies the sound: hé drifted to xiē with regular h/x alternation and onset shift.
曷 is the literary interrogative 'why, when' (now mostly archaic). Same phonetic gives
喝 hē (drink) and
渴 kě (thirsty),
歇 xiē — a tight phonetic family. The
日 over
匃 inside
曷 doesn't carry meaning here, only sound.