奥
おく · oku · JLPT N3 · noun
inside
🏠 oku sounds like a nook: the inner corner tucked deep inside a house
The old form 奧 has a roof on top and hands reaching into the far corner beneath it. That is why 奥さん (okusan, wife) originally meant the person of the inner rooms, and 奥歯 (okuba) means the back teeth.