pearl that is not quite round
璣 centers on a pearl that is not perfectly round, describing an irregular or slightly misshapen gem.
璣 combines the jade radical 王 with the phonetic component 幾, which likely contributed the sound and the idea of smallness or irregularity. The exact historical development is uncertain.
The jade radical 王 on the left suggests a gem, while the right side 幾 looks intricate and uneven. Picture a pearl with a slightly bumpy, non-round surface.
For キ, imagine a key-shaped pearl that is not quite round: key -> キ, and the irregular pearl looks like a tiny key.