This character simply visualizes the shape of a gate. In the center is a door, flanked by a pillar on each side. Even today, these iconic entrance structures can be seen in abundance at sacred sites.
In this character, you can find the kanji for ‘EAR’ placed inside a grand gate, just like a ‘Torii’ at a shrine entrance. Therefore, this kanji means ‘HEAR.’ In its original sense, it represents listening closely to receive a sacred message from GOD.
Ancient people saw daytime as the realm of humans and nighttime as the realm of God. In that unseen time, they listened for divine messages. This is why this character represents ‘DARKNESS.