gems of pearls formerly put into the mouth of a corpse
琀 refers specifically to pearls or gems placed in the mouth of a deceased person as part of burial rites. It is a rare and culturally specific term with no broader abstract meaning.
琀 combines 王 (jade/pearl) with 含 (contain/hold in mouth), directly reflecting the practice of placing gems in the mouth of the dead. The exact historical development is uncertain, but the component relationship is transparent.
The left side 王 represents a precious gem or pearl, and the right side 含 means to hold in the mouth. Picture a pearl being gently placed into the mouth of a deceased person as a final offering.
For カン, imagine a can of pearls being opened for the burial rite: can -> カン, and the pearls are placed in the mouth.