chest, coffer, rice tub
匱 centers on a container for storing things: a chest, coffer, or tub for rice. The idea is a box-like receptacle that holds items securely.
匱 combines the enclosure 匚 (box) with 貴, which likely contributes the sound. The character represents a container or chest.
The outer 匚 is a box, and inside is 貴 (precious). Picture a precious chest or coffer holding valuable rice or goods.
For キ, imagine a key (キー) unlocking the chest: key -> キ, and the precious contents inside are safe.